'"' spirit? ^ySF.-v' 






TEACHERS' 
GEOGRAPHY 



TEACHERS' GEOGRAPHY 



MAN AND ClImATE 



WITH PRACTICAL EXERCISES 



NINTH PRINTING 



MARK JEFFERSON 

Michigan State Normal College 



Published by the Author at 

YPSILANTI ;; MICHIGAN 
1921 



Q- 



5^ X 



Copuright, 1921, by Mark Jefferson 



SEP '^9 1S2I 



0)r,iA627010 



■^X' 



^ WHERE PEOPLE LIVE 

~ 1. If Geography is concerned with the earth and man, as soon as we have some 
^idea of the distribution of land and water on our globe, it becomes of interest to know 
^where this man is. A glance at the map on the insides of the covers of the book is nec- 
essary at this point. The depth of shades on it corresponds to the density of the popula- 
tion of the various regions. Where the map is black the homes of men are close togeth- 
er, and the villages and towns occur every few miles in every direction, many men liv- 
ing in little space. The lighter shades, the ruled lines, correspond to regions where 
cities are scarcer and even towns and villages come at much wider intervals, and farm 
houses may be so far from neighbors and so lonely that the inhabitants are much less 
accustomed to meeting people and exchanging ideas with them. The dotted parts of 
the maps indicate regions of still fewer inhabitants, long stretches of wilderness interven- 
ing between men's homes. The blank areas are practically uninhabited, though crossed 
from time to time by the solitary hunter or prospector or wandering bands of nomads. 
2. A single glance at this map is enough to show how evenly men are scattered 
over the earth. One continent has a good many people almost everywhere, another has 
larger spaces empty than are lived in by men, and two others have their northern and 
interior parts unoccupied while people are crowded into their southeastern and southern 
parts, in one case huddled together closer than anywhere else in the world. Why should 
the people of Asia prefer one corner of their continent so noticeably? Why are the Aus- 
tralians so few and why do they cling so to the southeastern part of their island conti- 
nent, the corner that is farthest away from England? Yet the people are British and 
their trade is with England. Most of the steamers that go to Australia go from England 
through the Mediterranean, the Suez canal and the Red Sea and then pass around the 
greater part of the continent of Australia to get at these people in the southeast. The fact 
is that the real Australia, the Australia of the Australians, is just this southeastern part. 
Everybody knows of Europe as the home of many, many nations, and nations that 
have figured much in history, literature, art, and science. The map shows us that men 
have taken possession of more of that continent than of any other. Europe is the only 
continent with almost no desert spaces. Eighty-five per cent of the surface of the conti- 
nent is settled. The rocky, rugged uplands of its mountains and the frozen Arctic plain 
of northern Russia are the only parts of Europe that have no inhabitants in perma- 
nent homes. This is more noticeable in the light of the wide blank spaces on the map of 
the other continents, ranging from two and a half millions of square miles in Australia 
to nearly eight milhons in Asia, space enough for the whole continent of North America. 
There are not people enough in the world to settle Asia as closely as Europe is settled. 

3. The New World lands — the Amer- 
icas, South Africa and Australia — look very 
different on this population-map from the 
Old World lands. Why are they so thinly 
settled? Is it because they are new merely, 
because men have been going to them from 
populous Europe only for a few centuries? 
Probably there is something in this. It may 
be that some day there will be as many peo- 
ple in these lands as in similar areas in the 
old world. But we must not form hasty 



Settled 


Areas In Mill 


ons of Squane Miles 


Millions 






of peop 


e 






1917 




Inhabited 


Empty 


872 
134 


Asia 


9 


8 
5 


N. America 


3 


48 


S. America 


3 


4 


8 


Australasia 


i;, 


2i„ 


160 


Africa 


^l2 


2 


481 


Europe 


3 


% 


1703 




28 


221/4 



conclusions. Some of the newer parts of Europe are more densely settled than old 
Greece. Ruins found in central Asia and parts of Arabia prove that these places have 
been known to men for a very long time and still are very sparsely settled. Mesopo- 
tamia and most of North Africa have had time and history enough. Think of Egypt 
and Babylon and Persia and Syria and Phoenicia. Are they all thicldy peopled today? 
In general it is the lands about the Baltic and the North Sea, new lands all in European 
history, that far excel in density the historic shores of the Mediterranean. Italy is only 
an apparent exception to this statement. It is true that the only North Sea countries 
that have a densfer population are Britain, Holland and Belgium, but it is to geographic 
conditions that Italy owes this, geographic conditions that she shares with northern 
Europe, and of which other Mediterranean countries are deprived. The chief of these 
is a more abundant rainfall, more evenly distributed throughout the year. 

4. Tliere will be changes in the distribution of population in the new world as time 
goes on. There will be more people there, some of the thinly settled places wiU fill up 
and perhaps some regions will have fewer people than today. The state of Iowa, for 
instance, had fewer inliabitants in 1910 than in 1900. This will come about as people 
come to know better what parts of the new world are suitable for settlement, asid as 
means of communication make remote places more accessible. If we knew today all 
about the resources of every part of the world, we should know its geography. That is 
precisely what geography is concerned with. Of course no one does know fully, but we 
get much light in trying to see why men have thriven and multiplied so much more m 
some places than in others. 

5. Europe is more thoroughly peopled than any other continent because millions 
of vigorous, restless men have wandered over it for thirty centuries, looking for homes, 
and finding them everywhere. They have proven it a good place to live in by living 
there, as men have not been able to live in the whole area of any other continent. In 
Asia men live mostly in the southeast because they have found that they could not live 
in other parts. They have tried it but did not thrive there. In the central deserts old 
settlements have long since died out and in the cold north only a few very rugged indi- 
viduals can keep alive. Children rarely grow up, population does not increase and it 
does not seem as if more than a few wandering hunters can ever make their homes there 
with climatic conditions as they are. 

If we can make out just why men thrive in one place and perish in another we shall 
be learning geography. The question that interests us always will be what is the fitness 
or unfitness of this place for man? Although America has been known only four centu- 
ries, there has been some selecting of the better places, some leaving of those first reached. 
Florida has been known longer than Michigan, but is not so thickly peopled. Has its ter- 
ritory belonged to the United States as long? Has it had — does it now have — direct rail- 
road and canal lines by which immigrants could travel from New York? Nova Scotia 
and New Brunswick have been known longer, and are nearer Europe than Ontario, but 
they are much less populous. Have the forests of New Brunswick any influence? Do 
they help settlers find a home? We shall see that Ontario is better fitted for men, and 
we shall not know its geography until we know in just what respects it is fitter. In the 
new world the study of the country and the seeking out of resources has been very im- 
perfectly done as yet, partly because we have not had time to do it and partly because 



we have not had very much occasion to hunt for better places. There are few people in 
tJie new world countries as yet and there is much land. It is for that reason that people 
in the new world are richer than in the older countries. Land is abundant and cheap 
and everywhere in the new world people have paid more attention to getting more land 
than to finding better land. Where land is cheap wages are high, for a laborer will be 
able to have land of his own there and get his food from it rather than work for low 
wages. 

6. In North America why are men so fond of the southeast and the Pacific coast? 
A glance at the rainfall map (p. 18) shows how much it is like the population map. 
The rains seem to have a good deal to say as to where men shall live. When we call 
rainy days bad weather we are not thinking very much of our words. It would be the 
worst possible weather for us if we had no rainy days at all. 

In our continent the hundredth meridian sharply separates the arid west from the 
rainy east, everywhere north of the 30th parallel. ' The population map shows that the 
rainy east has a thin or moderate population, while the arid west is mostly scantily 
peopled. The rainfall data of these maps are the averages of many years. Sometimes 
one year or several years together are unusually wet or dry. About 1890 there were 
several unusually rainy years in western Kansas and many people settled there, think- 
ing they were going to have rain enough to raise crops, but the dry years came again 
and they had to abandon their farms. Less than twenty inches of rainfall in an aver- 
age year appears to be insufficient for farming without irrigation. But while it seems 
desirable to have from 20 to 40 inches of rain a year, there is no increase of population 
where the rain increases to 40 or 80 inches. Alabama, Georgia, and Mississippi have 
more rainfall than Ohio, Indiana, and Illinois, but fewer people. 

In most deserts or dry regions a little rain falls in the mountainous parts. Some- 
times a dam may be built in a deep valley behind which a great lake of water may be 
ponded up in time of rains, to be led out in canals to fields of good level soil in the des- 
ert and enable abundant crops to be grown there. This is irrigation. There is no magic 
about it. There is never water enough to irrigate the whole desert. In our West the 
engineers would not hope to irrigate more than one acre in ten of the arid lands, even 
if they could save all the water that falls. With irrigation water to depend on crops 
m,ay be grown with more certainty than when the farmer must trust the rain to come 
when he needs it, and the desert soils contain all their plant food, never having grown 
any crops. On the other hand the expensive dams and canals must be paid for out of 
the crops produced on the irrigated land. 

7. The small empty places in Florida and Central America are not due to defect of 
rain. The very densely settled areas are not found occurring with very heavy rainfall. 
It is doubtful if man's prosperity is favored at all by more than 40 or 50 inches of rain. 
For these reasons we shall caU rainfall of less than 20 inches a year scanty, over 20 suf- 
ficient, over 40 abundant, and over 80 excessive,. For the rest, the conditions in the 
different areas of dense population are pretty strongly contrasted. Man lives easily 
amid the exuberance of the tropics, in a fruitful land with a climate that imposes on 
him little need of shelter and clothing. So in the West Indies we find a very dense pop- 
ulation on many islands. The area of very dense population toward New England on 
the other hand is in that belt of energetic American life between Baltimore and Boston 



in which resides so much of American culture, thrift, and business; where there are so 
many large cities, so many great universities, so many associations with great men and 
great deeds in the history of the United States. South of the thirtieth parallel the rain 
falls from the Atlantic to the Pacific and men have no such east and west division as in 
Canada and the United States. The islands of rainfall that accompany the chief moun- 
tain ranges of the western plateaus are occupied by islands of population, which stream 
even beyond the rain belts along the river valleys that lead flood water out into arid 
country, and make agriculture possible with irrigation. 

8. Labrador is apparently well watered enough for occupation but there is little 
soil on its wilderness of rocks, as in most of the country north of the St. Lawrence and 
the line of Great Lakes between Lake Ontario and the mouth of the Mackenzie river. 
So along the Pacific coast of Canada and Alaska there is rain enough. Overmuch moun- 
tain and bare rock deter man from settlement. Norway, which has a similar position 
in Europe, has 96 per cent of her surface uninhabitable mountains. That is the mean- 
ing of the white places in Scandinavia in Figure 6. The picture from the west of Nor- 
way printed here shows how scarce the soil is in many parts of that country. So 
with abundant rains, Norway has only 18 people to the square mile in a continent where 
the average is a hundred. Yet even so moderate a peophng as Norway's — it would cor- 




Photo by Mark Jefferson 

Fig-ure 1. The Scant Soil of Norway 



respond to the dots of our diagram — has been the result of a thousand years of national 
life, during which the Norwegians have been searching out and utihzing every nook 
and corner that can be used. 




Figure 2. Ujiliihabited Switzerlanrt 

9. Switzerland too has many mountains whose slopes lack soil for farm crops. In 
those places no one can live, although Switzerland has a history reaching back of the 
Christian Era. The diagram printed here shows very plainly how the Swiss people have 
tilled every scrap of usable land in their country. Where the diagram is black no peo- 
ple live, so the white spaces are the homes of men. We see that most of the Swiss are 
massed in what they call the Central Plateau, between the low Jura Mountains on the 
west and nortliwest and the lofty Alps in the southeast, from Lake Constance in the 
northeast to the Lake of Geneva in the southwest. The threads of white in the southern 
black masses are the narrow, inhabited valley floors among the lofty Alps. The few 
black areas in the Jura Mountains of the north show how much rarer is really rugged 
and inaccessible ground in these more gentle mountains, where men live not only in the 
broad valleys but often on the gentle slopes and rounded summits, which afford good 
pasture in abundance and some fields of soil. 

The mountains of Alaska may some day have such threads of population along their 
broader valley floors, but as yet they have no inhabitants. In the eastern United States 
we see on Figure 5 how the population thins out on the Ozark Mountains in southern 
Missouri and on the Appalachian ridges further east. 



10. But all these are regions of abundant rainfall and there it is always noticed 
that the rugged, rocky slopes lack soil to support life. Such mountains repel men; in 
arid countries mountains attract because it is only in the mountains that arid lands 
have any rain. In the western United States the cooling lift tliey give tlie winds brings 
very welcome rain. There every mountain is a green place, wooded and grassed, an 
island in the desert expanse. Men live there of necessity, not on tlie mountains, that 
men rarely do, but in the valleys between, and therefore always in limited numbers. 
The mountain valleys support the people of the western states, but their population will 
never be dense. For however densely the valleys are settled there will always be use- 
less land above. Mexico City lies in a basin which has rather less than twenty inches 



of rain, but a dense population lives there because the basin is easily watered from the 
surrounding heights. 

11. Swamps and undrained regions, too, are difficult to use for homes and we see 
the population thin for this reason in the swamps along the Mississippi in Arkansas 
and Louisiana. Here is too much water, just as in the Everglades at the southern tip 
of Florida. 

Wlien the swamps occur in very warm countries, like Central America and Brazil, 
plants and disease germs may .thrive so much better than men that only highlands are 
inhabited. It is not exactly correct to regard this as due to the heat, for ,the tropics 
are not so much regions of great heat as regions of continuous warmth. Greater heats 
occur at the outer borders of the torrid zone than within it, but the lack of winter in 
the torrid zone makes the warmth enervating and is remarkably favorable to vegeta- 
tion. 

12. Men seek the heights in the tropic regions not directly because of the heat be- 
low, but rather because of the overwhelming luxuriance of the vegetation and the preva- 
lence of human ailments in the combination of heat and reeking dampness on the low- 
lands. To clear away the forest is a heavy undertaking even in our northern open 
woods. The opening up of Michigan was not to be compared for rapidity with that of 
the prairie states where the land was ready for the plow when the owner came to it. 
In the wet regions of the tropics the forests are inconceivably dense. To leave the 
trail is not merely difficult, it is sheer impossibility. Plants grow, not merely on the 
ground but on each other, until the whole space between the tree top and the ground 
is filled with a mat of interlacing growths. To make a clearing in such a tangle is a 
huge labor, to maintain it an endless one. Kipling in his "Letting in the Jungle" well 
conveys the idea of vegetation fairly obliterating a village. He teUs how the deer and 
the wild pigs of the jungle had eaten the crops and trampled the fields. The elephant 
Hathi and his tall sons had torn the roofs from the huts and pushed down the village 




Photo by Mark Jefferson 

Figtu-e 3. In the woods on Mt. Misery, St. Kitts 
WHERE COULD ¥0U WALK IN WOODS LIKE THESE? 



walls just as the rains began — "a month later the place was a dimpled mound, covered 
with soft green growing stuff; and by the end of the rains there was the roaring 
jungle in full blast on the spot that had been under plow not six months before." 
(The Jungle Book.) 

From southern Nigeria we hear that the site of a town destroyed 60 years ago 
has been covered with a mahogany forest, some of whose trees are more than 10 feet 
in diameter. Perhaps the day will come when these forests must be tamed, but in 
America four centuries of Latin' dominion has made no impression on them. Dominica 
in the West Indies is as impassable off the narrow road as when Columbus gave it a 
name. 

13. It cannot be accident that the peopling of Australia, South Africa and Mada- 
gascar is all to the east. Let us see therefore what peculiarity each of these 
has in its eastern parts. Each (see p. 18) has abundant rain on the east, steadily dimin- 
ishing to scanty on the west. A glance at some political map of South Africa is instruc- 
tive. On the west, reaching from the Atlantic more than half-way across the continent, 
are the great deserts of Southwest Africa and Bechuanaland, then succeed for another 
considerable distance the semi-arid uplands of the Boer country further east, now 
Orange River and Transvaal colonies, and then, under the rugged slopes of the Drak- 
ensberg, by which the plateau breaks down on the east, the well-watered gardens of 
Natal. This thrice repeated group of features is a proper characteristic of an upland 
on which blow winds from an ocean to the southeast. 

It is not by chance that our people thin out so suddenly at the hundredth me- 
ridian, that the Pacific coasts of America are populated for thirty degrees on each side 
of the equator, then desert for the next ten degrees toward the poles in each hemi- 
sphere, thence peopled again beyond the forties. Surely the great things in geography 
are the agencies that have governed such a distribution of mankind. 



14. Upon careful examination of data that are now fairly obtainable for the whole 
world, at least as far as broader features go, it appears that the first requisite for a 
great population group is to have broad soil-covered plains for their homes; the second, 
suff'cient rainfall on these plains; and third, a temperature neither too low for plants 
nor so steadily warm as to enervate men and to provoke vegetation to become man's 
oppressor rather than his servant. History reveals man in the old world settling down 
more and more firmly and growing more and more prosperous under these conditions. 
The new world has many a hint of similar tendencies. 

In the matter of rainfall Europe is singularly happy. She suffers less from drought 
than any other continent. Only the Spanish interior and southeast, and the steppes of 
east Russia are too dry to have many inhabitants. Thus it happens that Russia's pop- 
ulation leans so decidedly westward as the map shows and that of the Iberian penin- 
sula is so close a reflection of its rainfall and therefore marginal. Its areas of excessive 
rain are very small. 

So much of Australia is arid that only its eastern border can ever become populous. 



8 

15. The distribution of people in South America is somewhat peculiar. It has few 
people. The densest population is rather over twenty-six to a square mile, that is, a 
little more than the average density of the United States. The patches of moderate 
population are at once seen to lie always within 400 miles of the sea. A northeast- 
southwest line through the center of the continent would have a region to the south- 
east with almost all the patches on the coast; another to the northwest with none at 
the coast, but all near it. What determines this arrangement? The mountains of the 
continent; for South America, though endowed with two of the greatest river systems 
of the world, leaves the greatest of these solitary and deserted and finds its mountains 
all-determining for the home of the nations. A glance at the map showing relief reveals 
the fact that the populations of the northwest lie along the high valleys of the Andes, 
and that the thin peopling, indicated by the dots, observes a similar behavior down to 
the tropic of Capricorn. In Peru and Venezuela the moderate population reaches the 
coast, while in Colombia and Ecuador the transition is from moderate along the central 
Andean chains to thin at the coast and scanty on the plains of the Amazon. 

16. The vast basin of the Amazon is seen to be all but deserted. Brazil has its 
people gathered along its eastern border, where it, too, is high, but the people havfe not 
drawn away from the coast as they have on the Pacific. Tropical South America has its 
people in the five mountain republics of the northwest — Venezuela, Colombia, Ecuador, 
Peru, and Bolivia, and on the elevated eastern sea border in Brazil. The Amazon basin 
is a great hinterland on which all have claims, for the most part ill-defined or in dis- 
pute, but in which none have any significant number of citizens. It is in complete pos- 
session of aboriginal savages; except for some isolated trading posts along the water. 
The equatorial position, of course, is the cause. The dominant races seek the moun- 
tains to escape from the heat and moisture of the lowlands. The tropical Andes are the 
great rain producers of their continent in the cooling lift they give to the trade winds 
that blow from the Atlantic against their eastern slope, but their upper valleys are 
drier and are the truly temperate regions of the world. North of the twentieth parallel 
South America hardly knows greater differences between summer and winter temper- 
atures than five or ten degrees. A lowland heat of 70 to 95 degrees proves very favor- 
able to rubber, sugar cane, coffee, and cocoa, but man ever since Inca days has pre- 
ferred the drier, cooler mountains, always with the same narrow range of tempera- 
ture. In the Andean republics the denser populations live where the thermometer 
ranges mostly between 35 and 70 degrees. 




'July 



3/1° 'S^. 1 1 000^ Cuzco 



_ioo 




I5O0- I 



Arg.Rep. Cordoba srs-^ 



Figure 4 

Hottest and coldest months, actual daily hot- 
test and coldest hours at Ypsilanti, Mich., 
Manaos on the Amazon, Cuzco in the Andes, 
and Cordoba in flat pampa of the Argentine 
Republic. 



At Manaos on the Amazon the 
hottest month is September. In 
the afternoon the temperature 
often reaches 97° or 98 with 
early morning temperatures of 
70" or 80". In June, the coldest 
month, the afternoons are from 
80" to 90" with early morning 
temperatures from 70 to 85 \ 

Figure 4 shows the highest and 
lowest temperatures for every day 
of the warmest and coldest 
months in 1916. It is warm at 
Manaos all the time, though there 
were moments of greater heat at 
Ypsilanti in 1916. The record is 
very different from the summer 
and winter one at Ypsilanti. It is 
tropical weather. 

Cuzco at 11,000 feet in the 
Andes has much the same sort of 
temperatures but 30" or so cooler. 
The warmest and coolest months 
are still so much alike that the 
thick and thin lines that represent 
them are closely entangled. Oc- 
tober is the warmest month, July 
the coldest. There is nothing 
summer-like about the Cuzco Oc- 
tober though, with temperatures 
running up to 65" or 70" 
only at the most, and nights at 
40", in July freezing every night. 
But there is the same monotonous 
uniformity as at Manaos and that 
is the characteristic of tropical 
weather, which may, it appears, 
be chilly but not variable. 

At Cordoba, in the central part 
of the Argentine Republic, sum- 
mer and winter are almost as weU 
defined as at Ypsilanti. 

January temperatures run 
above 100 and July nights often 
run below freezing. Spells of 
weather, now warm, now cool arc 
perceptible. The distinctness of 



10 

winter and a brief summer heat, that may be more intense than in the torrid zone, 
characterize the temperatures of the temperate zone. 

17. South of the tropic the Andes serve to part men as well as the waters. The 
high valleys there are too bleak for permanent homes. There the Andes are a wall, a 
boundary. They are not so much in Chile and in the Argentine, as east of Chilei and 
west of the Argentine RepubliG, a relation entirely different from that which prevails 
further north. The lowlands in the south have distinct summers and winters, hot and 
cool respectively. They are somewhat short of moisture, notably in the western Argen- 
tine plains, under the wind shadow of the Andes, for in this region of westerly winds the 
rains come from the Pacific or from disturbances that sweep eastward across the con- 
tinent. The plains here, narrow in Chile, broad in the Argentine, are the home of pros- 
pering, thriving men, of communities that are taking part in -modern life, with schools, 
railroads, and active commerce, that put them in contact with the other active people 
of the earth. 

18. There are not very many people in the world in comparison with its area. 
Texas would hold them all and give each man, woman, and child a square seventy, feet 
on each edge. They could stand much closer than that. Two thousand people can 
stand in a mile-long line very easily. They will have two and two-thirds feet l^etween 
the centers of their bodies. A square mile so covered would have four millions on it, 
and the whole sixteen hundred milhons of the world's people could stand in the little 
state of Rhode Island, and have abundant room to spare. But standing room is a very 
different thing from living room or "Sustenance Space," the area from which a man 
can draw his food and clothing. This varies greatly with the man's occupation, being 
very large for hunters and fishers, smaller for grazing nomads and lumbermen; small- 
er stiU for agriculturists. Thus it happens that there is a close relation between den- 
sity of population and the occupations widely prevalent through a region. Generally 
these relations hold over the world except in India, China, and Japan. Thus hunting 
and fishing may support from 2 to 8 people per square mile, and they must of course 
be savages or barbarians, lacking as they do agriculture and the manufacturing arts. 
Grazing and lumbering may prevail with densities of 8 to 26 people. So all four of 
these occupations are likely to occur iii one part or another of the dotted areas of the 
map (Figure 5, see numbers on the Legend) . The student should check this up some- 
what for himself by examining regions where he knows that lumbering, for instance, 
is general to see what the map indication is there. 

19. For agriculture, predominant where the population densities are from 26 to 
250, we distinguish two types. These might be called large-farm and small-farm agri- 
culture, but better names are extensive and intensive agriculture, putting the emphasis 
on the degree of thoroughness with which the ground is worked. The extensive or large- 
farm agriculture characterizes regions where the density of population is from 26 to 125 
persons to the square mile. This is typical of southern Michigan. Here the farm house 
is apt to have four indwellers, and the numbers allow from 6 to 31 such farms in a 
square mile. Each farm must run therefore from 106 to 20 acres in size; as a matter of 
fact we know the intensive farming which is prevalent with population densities of 126 
to 250 people to the square mile implies farms of 10 to 20 acres. They will be more 
thoroughly tilled and will yield larger crops for the same area. But the crops cost so 



11 

much to produce that they cannot compete in price with the crops raised on cheaper 
land by extensive methods. Note the following figures from the 1909 Year Book of the 
U. S. Department of Agriculture. They are averages for the twenty years 1889-1908 of 
the yields of five important crops in bushels per acre for the United States (extensive), 
and Germany and United Kingdom (intensive): 





U. S. 


Germany 


U. Kingdom 


Potatoes 


90 


107 


166 


Wheat 


14 


29 


33 


Oats 


29 


50 


45 


Barley 


56 


34 


35 


Rye 


16 


25 


27 (Ireland) 



It must not be supposed that extensive agriculture is bad agriculture. The table 
shows a German acre of land yielding about as much as two of ours. It involves more 
than twice as much labor though, each added bushel of yield costing a greater and great- 
er increase of labor. Where land is cheap and labor dear, as with us, extensive farming 
is appropriate. Two-thirds of our farms are of more than 50 acres and of Germany's 
four-fifths are of less than 25 acres. Moreover in England only the best farm land is 
tilled at all. 

20. For densities of population above 250 per square mile the predominant pursuits 
are the manufacturing industries except in eastern Asia, where an agriculture so in- 
tense prevails that there is nothing like it elsewhere, with the population running to 
1000 and 2000 to the mile. 

The manufacturing in districts with over 250 people to the square mile usually 
employs materials from a distance. Its power is often obtained from coal that is mined 
in the neighborhood. 

The densest type of population the world over is the city, made up wholly of men's 
dwelling places and working places at other than farm or field labor. The houses are 
many stories high and close together so as to wall in the street on either hand. Every- 
thing is planned for many people: streets paved for much traffic, stores planned for many 
buyers, banks for many persons' deposits and loans, hotels for ma.ny visitors, warehouses 
for the storage of much goods, factories for making enormous output of warcsi, vehicles 
for the transportation of many people, and lights and policemen to guard against the 
many evil persons in so great a crowd. 10,000 people to the square mile may be taken 
to signify a population so dense as to show all this. If parts of many incorporated cities 
have less it means only that they have their suburban and even country parts within 
the charter limits. In the outer part of Chicago are farms and although this is politic- 
ally city, it is really country after all. 

21. DISTRIBUTION OF POPULATION IN NORTH AMERICA. Fig. o 
Scale of Itliip: 042 miles to nn inch 

1. What one word best describes the density of population of North America north 
of the 50th parallel? 2. Has Canada more thin population north of 50 or scanty south 
of it? 3. In what states does a very dense population occur? 4. Name seven regions 
of dense population. 5. About what proportion of the United States is moderately peo- 
pled? Where? 6. How do the scanty and thin grades of population compare in area 
west of the 100th meridian? 7. Compare the density of population in the United States 
Ccist and west of the 100th meridian. 8. Explain (7) by Rainfall map. 9. Describe 



12 

and explain the density of population of Florida. 10. What is the principal grade of 
population south of the 30th parallel? 11. Why is there not the same difference at the 
100th meridian in Mexico as in the United States? (See Rain map.) 12. Describe the 
east and west arrangement of grades of density of population in Central America and 
explain it. 13. What style of agriculture appears to be most prevalent in North 
America? 14. Describe the density of population along the Pacific coast from Van- 
couver Island to Lower California. 15. Explain it. 16. In general how well are the 
West Indies settled? 17. Why is northern Mexico so thinly peopled? 18. In what 
river valley do the people of Canada mostly live? Why? 19. Where are the main 
agricultural regions of the United States? 20. What appear to be the occupations of 
northern and southern Michigan? 21. What five states have the largest area of scanty 
population? 22. Wliat five are the most uniformly moderately peopled? 

22. DISTRIBUTION OF POPULATION IN EUROPE. Fi^. 6 
Scale of Map: 508 miles to an inch 

1. Name the countries in whicli lies the largest area of very dense population. 
2. Locate the two next largest areas of very dense population. 3. In what six coun- 
tries are the largest areas of scanty population? 4. How many and what countries 
have very thin population? 5. What two grades of population density are most wide- 
spread in Europe? 6. What two occupations appear most prevalent in Europe accord- 
ing to the data of this map? 7. What is the chief occupation in Hungary? 8. What 
is the chief grade of population on the shores of the Baltic? 9. What is the highest 
grade of population density on the shores of the North Sea? 10. What grade of pop- 
ulation occurs on the mountains of Italy? What on the lowlands? 11. Describe the 
distribution of people in the Iberian peninsula? 12. What eight countries have most- 
ly dense, or dense and very dense population? 13. Wliat is the most strilting con- 
trast between the location of the more densely settled regions in Great Britain and the 
Iberian peninsula? 14. Compare the density of population in eastern and western 
Europe. 15. Compare the population density along the 40th and 50th parallels. (Fig- 
ure 9 has the parallels numbered.) 16. In what three countries do the population 
densities accord best with the data of the rainfall map? 17. About what point is 
Scandinavian life centered? 18. What sort of agriculture prevails in Italy? 19. What 
appears from the map to be the chief occupation in England? In northwest Scotland? 
20. What five mountain ranges show plainly in tlie population map? 21. How do 
they show? 

23. DISTRIBUTION OF POPULATION IN ASIA. DIAGRAM ON INSIDE COVERS 

1. Name four countries or colonies of very dense population. 2. Locate and de- 
scribe the five largest areas of scanty population in order of their size. 3. What Amer- 
ican population group corresponds in its position in its continent to that of China in 
Asia? 4. Wliat ones to Asia Minor and Palestine? 5. Describe the distribution of pop- 
ulation in Japan, India, and China. 6. Are the rainiest parts of China the most popu- 
lous parts? 7. Are the driest parts of China the least populous? 8. How well occu- 
pied are the parts of China that have sufficient or abundant rain? 9. What grade of 
population exists in the regions of excessive rain in India? 10. Is that also true in 
other continents? 11. In general why are the inhabited parts of Asia in the south and 
east? 12. Judging by density of population where is grazing most carried on? 



13 




Figure 5 



14 




3 



15 




^ 






a 
a 
o 







Flaiue. 9 



17 
24. DISTRIBUTION OF POPULATION IN AFRICA 

1. Describe the areas of scanty population. 2. What does the map of annual 
rainfall show there? 3. Where is the most densely settled part of the continent? 4. 
Has it rain? How do the people manage to live there? 5. Why is Madagascar most 
populous in the east? 6. In general how well do the rain and population maps of 
Africa correspond? 7. To judge by density of population what are the main occupa- 
tions in Africa? 8. In general how is Africa settled? 9. Why has Morocco less popula- 
tion than Algeria? 10. Why has Uganda more population than British East Africa? 

25. DISTRIBUTION OF POPULATION IN SOUTH AMERICA 

1. How wide is South America's strip of thin-to-moderate population? (The 
spaces between parallels in all parts of the maps are about 700 miles.) 2. In what 
portion of the continent is this strip? 3. MTiat is its re'ation to the region of exces- 
sive rainfall? 4. Where do most of the people of Brazil live? 5. In general what grade 
of rainfall is most often associated with considerable population? 6. What countries in 
South America have strips of moderate population on the coast? 7. What countries 
have moderate population in the mountains? 8. What countries have but two grades of 
population density? 9. Where do most of the Chileans live? 

26. DISTRIBUTION OF PEOPLE IN AUSTRALIA 

1. What fraction of Australia has scanty population? 2. About how many square 
miles of inhabited area has Australia? (See areas in the margin of the northern hemi- 
sphere of the rainfall maps.) 3. In what respects does the distribution of population 
fail to agree with the rainfall map? Why should the Australians, who are almost exclu- 
sively British, object to living in northern Australia? What are the probable occupations 
of Australia's people? 

27. ANNUAL RAINFALL, NORTH AMERICA. Fig. 9 

1. What parts of the map show rain where no men live? 2. Why is this? 3. 
What meridian is the rainfall boundary in the United States? 4. Describe the rainfall 
of Canada. 5. Describe that of Mexico. 6, What is the shape of the scanty rain 
area? 7. What percentage of the total area of the continent is made up by areas with 
more than scanty rainfall (include the islands)? 

28. ANNUAL RAINFALL, EUROPE. Fig. 8 

1. Is there any region of sufficient annual rain where the population is scanty? 
2. About what grade of population corresponds to the large area of scanty rain? 3. 
What grade of rainfall prevails in the parts of Europe most densely populated? 4. Com- 
pare the distribution of rainfall in the Scandinavian and Iberian peninsulas, noting the 
direction of diminution of the rainfall. 5. Does Eui'ope's abundant rainfall mostly cor- 
respond with the denser population? 6. Which is rainier, east or west Europe? 7. 
Which more populous? 8. What percentage of Europe has sufficient and abundant 
rain? 

2!». ANNUAL RAINFALL, ASIA. Fig. 10 

1. Where is there excessive rain? 2. How much of Asia is dry? Where? 3. Lo- 
cate the sufficient rains. 4. Describe the distribution of rainfall in India. 5. How 
well does it agree with the distribution of people? 6. Explain the distribution of pop- 



18 



ANNUAL RAINFALL OF THE 




SHADE 


RAINFALL 


ick 


Excessive 


led lines 


Abundant 


ts 


Sufficient 


ink 


Scanty 



Figure 10 

LEOEND 

DETAILS 
An annual rainfall, including melted snow, of over 80 inches. 

An annual fall of from 40 to 80 inches. 
An annual fall of from 20 to 40 inches. 

Less than twenty inches in the year. 



19 



WORLD (INCLUDES MELTED SNOW) 




l''igure 11 



After Ilerbertson 

In the blank areas agriculture is hardly possible without irrigation. Within them 
lie all the world's deserts. 



20 

ulation in connection with rainfall in the northernmost of the Philippine Islands (Lu- 
zon). 7. Compare the rainfall and population of eastern and western Turkey. 

30. ANNUAL RAINFALL, AFRICA. Fig. 10 
1. Wliat percentage of Africa is dry? 2. Compare it with Europe in this respect. 
3. Where is Africa's excessive rain? 4. Compare the distribution of rainfall in north- 
ernmost and southernmost Africa with that of people. 5. Does Africa anywhere show 
denser population where the rainfall is excessive? 6. Illustrate. 

31. ANNUAL RAINFALL, SOUTH AMERICA. Fig^. 11 

1. Locate areas of excessive rain. 2. How much of the continent is dry? 3. De- 
scribe the larger area of scanty rain. 4. What is the population grade along it? 5. 
How does South America compare with other continents in the general supply of rain- 
fall? 6. What four countries have each four grades of rainfall? 7. Describe the rain- 
fall of the Argentine Republic and Chile. 

32. ANNUAL RAINFALL, AUSTRALIA. Fig. 10 

1. What proportion of Australia is dry? Where? 2. Where are the excessive 
rains? 3. How does Australia compare with other continents in raininess? 4. ^Aus- 
tralia and the United States have about the same areas, how do their rainy areas com- 
pare? 5. Which is rainier: New Zealand, Tasmania, or Victoria? 

The student who has worked his way to this point will see the great control over 

man and his occupation that is exercised by rainfall. We shall now set forth the chief 

principles on which the distribution of rain depends. This involves a brief study of 
climate. 

THE GENERAL CAUSE OF RAINFALL 

Rain is caused by the cooling of water vapor in the air. In far the greater num- 
ber of cases, the cooling is caused by some upward movement of the air. Not rising 
any more than one would speak of a pendulum rising at the end of its swing. But 
there is an upward element in the movement of the wind over the surface of the 
earth, when it comes to mountain slopes, in the equatorial regions, and in the cen- 
tral regions of the cyclones of the Temperate Zone. This upward movement brings 
the wind where there is less air above it, it expands, lifts the air above it, is cooled, 
and if there is enough water vapor present, rain results. 



21 

CLIMATE 

33. We shall get no clear idea of the dimate of distant lands unless we know 
something about our own. We shall find no difficulty in picturing in our own minds a 
snowstorm in Russia or a thunderstorm in Havana, for we are pretty familiar with 
others much like them at home. To get an idea of the dust storms of the desert is not 
so easy, but if we observe carefully the dusty squall that often precedes our summer 
thunderstorms and think of them lasting much longer, with the wind sweeping over 
plains of bare earth and sand, we may build up some notion of the thing, especially if 
we will further read good accounts by eyewitnesses. Successful imagining must have a 
basis of known fact for comparison or contrast. To grasp the important idea that the 
tropics are monotonously warm, important because the inhabitants of those regions are 
not men of famous deeds, as if some stimulus for ambition were lacking there — it will 
help wonderfully to observe with some closeness how incessantly our weather goes from 
extreme to extreme. If the mind then attempts to conceive a continued warm spell, 
varied only by the addition of months of wet — not passing showers — ^^and followed by 
other months of steady drought, one realizes something of the debilitating effect of 
tropical climates, and perceives perhaps the better the stimulus we are under from the 
great weather changes of our miscalled Temperate Zone. 

The local weather map is therefore the appropriate material for the study of cli- 
mate. By its aid we may extend our direct observations to much of North America. 

34. Climate and weather reside in the lower air. Events above are of great im- 
portance, but the region of study is the lower air which we breathe, in which our bodies 
are constantly bathed, at the bottom of the ocean of air. 

The conditions of the lower air that concern us are chiefly: TEMPERATURE, 
PRESSURE (much air or httle air), MOTION (winds), and the PRESENCE AND 
CONDITION OF WATER (rain, clouds, dew, and frost). 

TESrPERATURE OF THE LOWER AIR 

35. You will henceforth observe each morning at as early an hour as you are in 
the habit of going out of doors, how the temperature compares with that of the day be- 
fore. It should not be supposed that the reading of the thermometer replaces this exer- 
cise for the student. It is perfectly possible to read the thermometer and record its in- 
dication in the book without ever thinking what it means. It is desired that the student 
come to class with a mind active with regard to the weather. The daily consideration of 
the question whether it is warmer or cooler than the day before or whether the tem- 
perature is not perceptibly, different, will be found useful. A sufficient record is one of 
the words, "warmer," "colder," or "stationary." Any doubt is to be covered by the use 
of the word "stationary." It will appear very soon that the characteristic of our 
temperature is change — change through the day, change through llie year; and 
change from day to day, apparently regardless of seasons. In what follows we 
look for the causes of this changeability. 

EXERCISE 1.— TEMPERATURE OF GROUND AND AIR 

36. On a cloudless day take the temperature of some dirt that has been dried and 
exposed to sun and air for some time. It should be set out early in the morning on the 



22 



ground, a little away from any building in such a way that the sun will get at it all day. 
If no such place is available put it in one place for the morning sun and in another for 
the afternoon. The thermometer should have a cylindrical bulb which is just covered 
by a thin film of dirt as the thermometer hes on the dirt in the pan. Dealers in physical 
instruments have a cheap German thermometer that is good enough for the purpose. If 
it can be done safely, it is well to leave the pan and thermometer out aU night when 
there are no signs of rain. A few night observations by the teacher and some of the 
more enterprising students will add to the interest. The thermometer in the dirt should 
not be touched but lie always undisturbed. Each student should make three readings of 

this thermometer, and another that hangs, shaded, 
in the air nearby, at intervals of not less than an 
hour and a half between the readings, and note the 
results neatly on the table. 

K the dirt is kept dry the pan of dirt may be 
used to show insolation in winter as well as in sum- 
mer, and on very cold days when there is snow on 
the ground the class will be much surprised to no- 
tice that a thermometer placed in a pan of snow 
with its bulb buried in snow registers temperatures 
so cold and yet so much above the temperature of 
the air. Thus, on February 12, 1914, we found at 
Ypsilanti, at 7, 9, 11, 1, 2, 3, and 5, the air had tem- 
peratures: -6.3, -0.5, 6, 11.5, 12.5, 10.5, 5, while the 
snow showed: -7, 5, 15, 27, 27, 21.5, 10. The day 
was clear and almost without wind. 





Temperatures 


Hour 


Dirt Air 


5 






6 






7 






8 






9 






10 






11 






N 






1 






2 






3 






4 






5 






6 






7 






8 






9 




10 




11 





37. To judge from your observations of the temperature of the dirt in the pan and 
of the air, which heats up more rapidly, ground or air? Does it also heat up to a great- 
er degree? Does either get as hot at one as at noon? Which cools off faster? How do 
our observations show this? How would the observations of a cloudy day differ from 
these in the daytime? In the night? Try it. Can you teU why dew and frost are not 
formed on the ground on cloudy nights? 

From the readings of the thermometers gathered by all the class members and an- 
nounced in the class discussion, fill out the whole of your table. 

38. Physically the heat of the air consists in the rapidity of the vibration of the 
particles; the faster they go the hotter the air. So, too, of the ground, its heat consists 
of the rapidity of the vibrations of its particles. Heat is communicated from one body to 
another in two ways, (1) by conduction, when the bodies are close together, (2) by radi- 
ation at all sorts of distances. It is believed that it travels not as heat but as vibrations 
of all-pervading ether*, which occupies not merely space but extends through all gases 
and even other bodies. The insolation then comes to us from the sun as vibrations of 
the ether which do not heat the air much in passing through it. So the radiation from 
the earth into the upper air and space is by the same sort of vibrations of the ether, 
which do not materially warm the air in passing through. Conduction, on the other 
hand, is illustrated by the warming of the air from the ground on which it rests. The 



*LO'DGE— The Aether of Space. Nature, January 14, 1909. p. 322. 



23 

ground being warmer than the air, its particles are vibrating faster than those of the 
air. They are therefore supposed to hurry the adjacent air particles along in their 
swings until those too go more nearly at the same rate as the earth particles. Of course 
in doing this they lose some of their own speed and the result is a cooler earth as well as 
a warmer air. In usual language we say heat has been conducted from the ground to 
the air. And all the time that the lower air is being warmed by conduction heat is radi- 
ating away from the ground througlt it to be lost in space, without much effect on the 
air on the way. For conduction one body must be warmer than the other, but radia- 
tion goes on all the time from cold bodies as well as hot, though its amount is propor- 
tional to the temperature. A hot body radiates more heat than a cold one. And so sum- 
mer and winter, day and night, in cold and heat ahke, heat is radiating away from the 
earth, just as on all clear days insolation comes to the earth through warm air or cold. 



39. The effects of the sun's rays are different according to the thing they fall on. 
Clear air allows them to pass through with little effect on it, so that a good deal of inso- 
lation reaches the surface of the earth below. If this is land it heats up rapidly; if 
water, much less, since the rays pass through water somewhat as through air, although 
less freely. Anyone who has bathed on a sandy shore knows how strongly bits of stone 
or metal become heated in the sunshine, far more than water ever does. Shallow waters 
attain a more agreeable temperature than deeper water, because the rays are able to 
pass through and warm the bottom, which warms the water in turn. The waters of 
Lake Erie, which is shallow, become quite warm in summer, those of Lake Superior, 
which is deep, are always icy cold. The land surfaces are thus seen to be most sensible 
to the sun's warming power. For one thing the effect on solids is confined to the surface 
layers. At a very moderate depth below the surface of rock or dirt exposed to the sun- 
light, no warming at all occurs. At a desert station in Turkestan, the mean temperature 
of the ground in the heat of the day, is 90°, but just before sunrise, 41°. Sixteen inches 
under ground the temperatures are 58.5° and 57.5°, respectively, almost a uniform tem- 
perature from day to night. Most of the heat is concentrated in the five or six inches of 
depth just below the surface. In the water the penetration is far greater. Some lakes 
in the temperate zone are warmed by the sun's rays as much as forty feet below the sur- 
face. The' effect is therefore distributed through a mass of water so thick that each com- 
ponent layer is but little warmed. Moreover, a great part of the effect of the sun's rays 
on the water surface is used in evaporation, without causing any sensible rise in tem- 
perature. Finally, water is a very hard thing to warm. From all of these causes it re- 
sults that the ocean surface, or the surface of a deep lake is slow to warm and slow to 
cool. So lake and ocean shores are cool places in summer and rather mild in winter. 



40. Clean air is so transparent to insolation, that at time when the sun is high, 
three-fourths of the sun's heating power may become effective on the ground after pass- 
ing through the whole depth of the air. Mainly, then, it is the dry land that is warmed 
by the sun. The most important point for the study of the weather is that the air is 
mostly warmed by the ground on which it rests and little by the rays of the sun that 
pass through it. The air temperatures never become so high as those of the ground. 
By what process does the ground warm the air (see 38)? 



24 





Temperatures 


Hour 


Air Dirt 


8 


30 


22 


9 


35 


52 


10 


40 


66 


11 


45 


76 


Noon 


49 


80 


1 


52 


81 


2 


53 


74 


3 


52 


58 


4 


49 


42 


5 


45 


39 


6 


43 


37 


7 


41 


35 



February 22, 1916, the following temperatures 
were observed in the air and on the surface of a .pan 
of dirt at Ypsilanti, Michigan. The day was clear 
till 3:30, when clouds came up. There was very 
little wind. 

How much warmer did the ground get than the 
air? When did the ground reach its greatest heat? 
What was the range of temperature — the difference 
between the least and the greatest temperatures — 
that day in the air? On the surface of the ground? 
It will be noticed that neither ground nor air was 
warmest at noon. 




Fianiie 12 



41. In general the heat received by the ground depends on the height of the sun 
in the sky. It is greater, therefore, at noon than in the morning, greater in summer 
than in winter, and greatest in the tropics where the sun at times stands overhead. Lpt 
the page of this book represent the su'-face of a town or city, as the book lies flat open 
on the table. In the torrid zone the sun shines down on it from above, and the buriclie of 

rays that touch the page is as thick 
through as the page is wide. At Ypsi- 
lanti, however, the sun shines on the 
page from .a point a little above the 
horizon, and a thin bundle, containing 
a few rays, spread over the same sur- 
face. Thus the thick bundle of tropical 
rays s s' (Fig. 12) renders much more 
heat to the surface in which A B is a 
line than the thin bundle of rays s" 
s"'; although each bundle is just wide 
enough to shine on the whole width of 

A B. In the United States, of course, the sun is never overhead, but its heating power 

is greater in proportion as it gets higher in the sky. 

42. One would naturally suppose that the greatest heat in the world occurs in the 
torrid zone but that is not the case. In 1912 climatic records were collected for the 
whole world for the first time, two records for each ten degree square of the lands, 
where they could be had. The highest temperature observed within five degrees on 
either side of the equator was 101 \ Between five and ten degrees north and south the 
highest temperature recorded was 107 \ Beyond 10 degrees north and beyond 10 de- 
grees south, at distances of over 700 miles from the equator, the high temperature of 
115 occurred or was exceeded at 19 stations, Baghdad, 33" from the equator, reaching 
117°. But the hottest points saw the thermometer rise above 120", and these points 
were all in the temperate zone: 

123.6 at Insalah, Africa, latitude 27" N. 
120.8 at Eucla, Australia, latitude 32" S. 
120.6 at Hyderabad, India, latitude 25" N. 
No less than 47 stations in the temperate zone experienced higher temperatures than 



25 



the zone within five degrees of the Equator, among them Kamloops, Canada, Yuma, 
Arizona; and Athens, Greece. 

The heat at any place depends on a number of factors besides the heiglit of the 
sun in the sliy. A very important one of these is the length of the longest day. This 
at the equator is twelve hours; all days are equal in length there. But 23' 30' away, 
at the Tropic of Cancer, it is about 13 hours, and the night lasts of course but 11. That 
is for June 21. The sun then is in the zenith for places on the Tropic, just as it is at 
the equator in March and September. The sun can be no higher. Now the equator in 
March and September has that zenithal sun for 12 hours, followed by twelve hours of 
night in which to cool off. At the Tropic the day lasts for 13 hours, and the night but 
11! As regions north of the Tropic have a still longer day, with a shorter night, while 
their sun, if no longer in the zenith, is still very high in the sky, it is not so strange that 
the highest temperatures are met with outside of the temperate zone. Ypsilanti at mid- 
summer has a fifteen-hour day, a nine-hour night, and the sun gets within 24" of the 
zenith. 

43. Only six miles above the surface of the earth the air stays about 55 below 
zero throughout the year, summer and winter alike, in the sunshine or in darkness, in 
the temperate zone or over the equator. There are differences of temperature up there 
it is true, but oh, so tiny! The thermometer may rise in summer to 49 ' below zero and 
in winter drop to 63" below. Bright sunshine may give a temperature one degree high- 
er than prevails by night, but we have learned beyond a doubt by sending up kites and 
balloons to which self-registering thermometers are attached, that the upper air is al- 
ways bitterly cold, colder than many of us have ever had any experience of. As was 
said, it always stays about 55" below zero. 

44. When we feel the uncomfortable heat of the noonday sun in summer, we must 
not forget that it has come to us through this icy upper air, and that it was in that icy 
.air the instant before it reached us. Light travels so fast that six miles is passed 
through in the tiniest fraction of a second. It is quite certain, therefore, that the sun's 
heat can pass through air without warming it very much. The air in which we live, the 
air next to the ground, is warmed almost entirely by the ground it rests on. For the 
sun's heat, that has so little effect on the air it passes through, heats the ground strong- 
ly, in summer to 168" and 170'. The heated ground, in turn, is the source of the heat of 
the summer air. When we say it is hot in summer, the "it" we refer to is the lower air. 
Its highest temperatures are noticed near the ground. The temperature on a high tower 
is usually a degree or more colder than near the ground. 

45. In the city of Paris, France, there is a graceful steel tower nearly a thousand 
feet high, the Eiffel Tower, from the name of its constructor. Thermometers are instal- 
led at top and bottom of the tower and have been 
recorded for many years. Here are some temper- 
atures for a summer day. 

What was the range of temperature at the top 
of the tower? What in the air below? That is 
nearly twice as much below as above, though it was 
not what you and I should call a hot day. It was 
not hottest at noon but after noon. At what hour? 
How much hotter below than above? 







Temperatures 




Air 


Air Dirt 


Hour 


at 1000' 


at base at base 





59" 


59 


1 55' 


4 


56 


56 


54 


8 


58 


64 


82 


N 


64 


70.5 


97 


2 


65 


71 


98 


4 


65.5 


71 


91 


8 


59 


60 


52 



26 



EXERCISE 2 

46. Figure 13 has a curve constructed to show the temperatures of the surface of 
the ground near the base of the tower that day. The vertical lines represent hours of 
the day and the horizontal ones every tenth degree of temperature. On the first vertical 
line, which stands for zero hours (midnight), we have put a dot half way between the 50° 
and 60° horizontal lines to represent the 55° of the right-hand column of the table, the 
temperature of the surface of the ground at midnight. On the second (4 o'clock) line 
the dot was put a little below half way from 50° to 60° to represent the 54° of the table 
at, 4 o'clock, and so on through the day. Finally a smooth curve was drawn through all 
the points. You will notice that the temperature is given for 2 p. m. as well as for noon 
and 4. Draw curves for the air temperature at the base of the tower with red pencil, 
and for the air at the top in blue pencil on the same diagram. Figure 13. 




Diagram of the temperature ^of 
the ground in Paris through a summer 
day. On this diagram each student 
is to place the temperature of the air 
at the foot of the Eiffel tower, ?'ed 
curve, and at the summit of the tower, 
blue curve. 



Figure 13 

Is it by day or by night that the three curves differ most? How much hotter did 
the ground get than the air? Why was the lower air six degrees warmer than the upper 
air at 2 p. m.? 

TEMPERATURES ON LAND AND LAKE 

47. This table gives the temperature of the air 
about as it is near Gaylord and at a point over the 
middle of Lake Michigan west of Traverse City on a 
very hot, still day in August and a very still, cold 
one in February. Construct curves for each, calling 
one square vertically two degrees and horizontally 
one hour. 1. What was the range of temperature 
in Gaylord in summer? 2. How much in winter? 
3. What were the temperature ranges over the lake? 4. Which place was warmer 
in summer? 5. Wliy? 6. Which was warmer in winter? 7. Why? (Probably 
Lake Michigan never freezes all across. This is the report of the masters of steamers 
which ferry freight trains across all winter from Ludington and Grand Haven. They 
sometimes encounter drifting ice floes and much continuous ice near the Michigan 
shore.) 8. Why did it never go much below 33' out over the lake? 9. Is 33° cold 







EXERCISE 3 


^TE 




Gaylord 


Lake 




Hour 


Aug. 


Feb. 


Aug. 


Feb. 





67° 


—4° 






4 


64 


—7 


57 


34 


8 


68 


—7 


60 


35 


Noon 


77 


4 


62 


36 


4 


81 


8 


62 


36 


8 


72 


3 


60 


34 


12 


69 


1 


59 


33 



27 



weather or mild, as winter weather goes? 10. Which probably has the milder winter, 
Traverse City or Gaylord? 11. Why? 12. Why has Milwaukee greater cold in winter 
than Grand Haven? Note that our winds are usually from the west, that is more of- 
ten than from any other direction. February 9, 1914 Milwaukee had four below when 
the air at Grand Haven was at ten above. The wind at Grand Haven was blowing 
twenty-five miles an hour from the west. The same morning Saginaw had six below and 
Saugeen ten above, and the wind at Saugeen was southwest thirty-five miles an hour. 
13. Why was Saginaw colder than Grand Haven and why are Saginaw and Alpena not 
summer resorts? 14. Why are the summer resorts of Lake Michigan along the east- 
ern shore? Name them. 

48. Over the ocean the air has a still smaller range of temperature. Half way 
from Newfoundland to Ireland the air in summer averages 60" and in winter 40°. 
The frequent west winds blow this mild ocean air, that is neither hot in summer nor 
cold in winter, over the western lands of Europe, giving them a mild climate, much 
less hot in summer and much less cold in winter, than in the same latitude in 
eastern Europe or in eastern America. 

Labrador and Great Britain are in about the same latitude, but Labrador is 
bathed in land air by the same west winds that bathe Britain in air from the ocean. 
So Labrador is hotter in summer and colder in winter. If there were warm water 
flowing along the coasts of Europe would it make the summers there cool? We have 
often been told of such warm water but an immense number of observations of the 
temperature of the water off the Irish west coast show that it does not exist. The 
variations are not great. The February temperature of those waters is 50 and the 
August temperature 60°. The winter temperature, 50°, is warm for winter, truly, 
and winds off it keep the winters very mild; but it is cold water. Even the summer 
water at 60 cannot be called warm. 

EXERCISE 4 

49. Draw four temperature curves from the data in the following table, which 
gives average hourly temperatures for summer and winter months at Ypsilanti and 
Cuzco. Put all four curves on a single diagram with one square of the quadrille paper 
vertically for 2° and one square horizontally for one hour. 1. Where is Cuzco? 2. In 

what latitude? 3. At what altitude? 4. Which 
place has the more temperate weather? 5.. 
How much warmer are summer days at Cuzco 
than winter ones? Cuzco has distinct wet 
and dry seasons, with 66 per cent, and 37 per 
cent, respectively, of cloudy weather. Now 
clouds have two effects on the temperature. 
They (1) prevent the sun's rays from reaching 
the ground, and (2) they prevent the earth's 
heat from radiating away. The 27th of Janu- 
ary, 1914, at Ypsilanti (see page 29) was 
clear and the 22nd was cloudy. The 22nd 
shows both (1) and (2). 6. Do clouds lift 
or lower the day part of the curve? 7. How 
do they affect the .night part? 8. How the 
daily range of temperature? 9. When has 





Cuzco 


Ypsilanti 


Jan. 


July 


Jan. 


July 





48 


38 


14 


65 


2 


47 


36 


14 


64 


4 


46 


35 


14 


62 


6 


46 


34 


14 


65 


8 


49 


41 


14 


68 


10 


55 


51 


17 


74 


N 


60 


57 


20 


77 


2 


59 


59 


21 


79 


4 


56 


56 


20 


77 


6 


54 


49 


18 


75 


8 


51 


44 


16 


72 


10 


49 


40 


15 


67 





48 


38 


14 


65 



28 

Cuzco less daily range? 10. When has Cuzco clouds and rain? 11. Is January or July 
summer at Cuzco? 12. Whicli curve should run among higher temperatures? 13. 
Which does run higher? Before considering the next question, construct a broken-line 
curve to represent the following temperatures at the hours of the table: 45", 43, 42, 41, 
48, 58, 65, 66, 63, 56, 51, 47, and 45. The curve may be put on the same diagram with 
the other two. It represents what the temperatures might be at Cuzco in January if 
the sky were cloudless. Clouds change this broken-line curve into the actual January 
curve. 14. Why do the January nights differ more from July nights than January 
days from July days? 

EXERCISE 5 

50. It will help toward clear thought if, in speaking of this afternoon maximum 
of temperature, we refer its time, not to noon, but to the thing which fixes noon; 
the sun's height in the sky. 

1. When in the day — in terms of the sun's height in the sky — is it hottest? AFTER 
THE MOMENT OF HIGHEST SUN. The sun is highest of ah the year for us on June 
21st, the summer solstice. 2. Wlien in the year, in similar terms to those just suggested, 
is it hottest? Let us now construct annual temperature curves for Cuzco and Ypsilanti, 
counting one square of the quadrille paper vertically for a degree and two squares hori- 
zontally for a month. We shall use the mean or average temperature of the whole 
month and consider the date that of the middle of the month. 



Cuzco Ypsilanti 

January 51 5 24 5 

February 519 23 

March 52.2 32.6 

April 51.3 46 3 

May 49.6 56.8 

June 46 6 66 1 

July 45 69.8 

August 48.1 67 7 

September... 49 9 61.3 

October 51 2 49 4 

November 51.8 36 8 

December 51.2 27.1 



3. At Ypsilanti at what date in the year is it hot- 
test? 4. At what date is the sun highest? 5. What is 
the time of greatest heat in terms of the time of high 
sun? The Cuzco curve is peculiar. 6. When does it .ap- 
pear to be hottest at Cuzco? Hottest must here be taken 
to mean hotter than just before and just after. In that 
sense could there be two hottest moments? - 7. How often 
is the sun high at Cuzco? 8. At what seasons, as we 
call them? 9. At that time at what point in the Cuzco 
sky is the sun? 10. When is ii hottest at Cuzco, with 
respect to the high sun? 11. Wliy are not the two high 
moments six months apart? The sun crosses the Cuzco 
zenith on the 12th day of February and the 30th day of October. 

51. The student should now add to his daily weather record the direction of the 
wind and the force of the wind as expressed in the Hazen wind scale. 

FORCE OF THE WIND 

— Calm. 1 — Moves leaves of trees. 2 — Moves branches. 3 — Sways branches, lifts 
dust. 4=— Sways trees, lifts twigs from ground. 5 — Breaks small branches. 6 — Destroys 
everything: hurricane. , 

52. The temperature of a day may be ascertained by averaging the observations 
of a thermometer read every hour, but so many readings are very troublesome to make. 
Where the expense of $25 does not prevent, an instrument like our thermograph gives 
good results with very moderate care. A much less expensive instrument ($5), that is 
little trouble to use, is the maximum and minimum thermometer, to be seen in our 



29 

laboratory and explained on page 60 of Davis' Meteorology. By referring to the temper- 
atures given in 53, we readily mal^e out the relation of the half sum of maximum and 
minimum temperatures to the mean of the tv/enty-four hourly observations. On Janu- 
ary 1, the minimum was 12 \ maximum 24% their half sum, 12 + 24-^-2 = 18. The mean 
of the twenty-four hour values is 19.1 . On the second the half sum is 4" to a mean of 
7.3". 1. How is it on the third, fourth, fifth, and sixth? 2. Make the same compari- 
son for the mean values at the bottom of pages 29 and 30. The two num- 
bers are usually within a degree of each other. For very many places in the world this 
is our only means of getting the temperatures. Those for Ypsilanti in 49 result from 
15 years of such observations. 



HOURLY TEMPERATURES AT YPSILANTI, MICHIGAN 

JANUARY, 1904 





MORNING 


AFTERNOON 




Jan. 


1 


2| 3 


4 1 51 6 


7 1 8 


9 


10 


1 11 1 N 


1 1 


21 


3 1 


4 1 5 1 6 1 


7 1 8 9 1 10 


11 1 Mt 


Mean 


1 


23 


24 


24 


24 


22 


22 


21 


19 


18 


20 


21 


22 


22 


22 


22 


21 


17 


16 


16 


15 


13 


12 


12 


12 


1971 


2 


12 


12 


11 


10 


10 


9 


8 


7 


7 


7 


7 


8 


9 


10 


10 


10 


10 


9 


8 


6 


2 





-2 


-4 


73 


3 


-4 


-6 


-7 


-7 


-8 


-9 


-8 


-7 


-5 





3 


5 


7 


9 


10 


10 


8 


7 


5 


5 


6 


6 


5 


5 


1.2 


4 


4 


2 


2 


1 





_'7 


-3 


-3 





4 


9 


11 


11 


10 


10 


10 


8 


7 


4 


2 


1 


-1 


-2 


-4 


3.4 


5 


-6 


-6 


-6 


-7 


-7 


-6 


-4 


-1 


2 


6 


9 


11 


12 


18 


16 


14 


14 


14 


14 


13 


13 


16 


16 


14 


6.6 


6 


14 


12 


12 


13 


14 


16 


17 


19 


20 


22 


24 


24 


25 


28 


28 


27 


25 


24 


23 


22 


23 


24, 


24 


24 


21.0 


7 


24 


25 


25 


24 


24 


24 


21 


20 


20 


20 


21 


?4 


24 


25 


26 


28 


29 


29 


29 


29 


31 


31 


31 


31 


25.6 


8 


32 


33 


34 


34 


34 


34 


35 


35 


34 


35 


35 


36 


36 


33 


33 


3i 


32 


31 


31 


30 


29 


27 


26 


24 


32.3 


9 


24 


22 


22 


23 


22 


22 


21 


21 


22 


22 


23 


24 


24 


24 


24 


23 


22 


22 


22 


22 


22 


21 


20 


14 


22.0 


10 


12 


10 


6 


4 


4 


4 


6 


9 


11 


13 


16 


18 


19 


20 


20 


20 


20 


20 


20 


20 


20 


20 


20 


20 


14 7 


11 


20 


20 


19 


19 


18 


18 


17 


15 


13 


12 


14 


15 


17 


18 


17 


17 


17 


18 


18 


19 


19 


19 


20 


20 


17.5 


12 


19 


20 


20 


21 


21 


22 


22 


22 


22 


23 


24 


24 


25 


25 


25 


25 


25 


25 


25 


26 


26 


25 


24 


24 


23.3 


13 


20 


22 


24 


24 


25 


26 


26 


26 


26 


26 


26 


27 


27 


26 


25 


24 


23 


23 


24 


24 


24 


22 


22 


21 


24.3 


14 


23 


24 


24 


24 


23 


23 


20 


20 


20 


21 


22 


22 


22 


22 


23 


23 


22 


22 


22 


22 


21 


20 


20 


18 


21 8 


15 


18 


18 


19 


18 


16 


17 


18 


17 


18 


21 


23 


25 


25 


25 


24 


24 


24 


24 


23 


22 


22 


22 


22 


22 


21.1 


16 


22 


22 


23 


23 


23 


24 


27 


28 


30 


31 


31 


30 


27 


23 


22 


20 


19 


18 


16 


15 


14 


13 


12 


12 


21.9 


17 


10 


11 


12 


13 


13 


13 


12 


11 


11 


11 


11 


13 


14 


14 


14 


14 


12 


12 


12 


11 


10 


11 


10 


7 


11 8 


18 


6 


5 


4 


4 


4 


4 


4 


4 


4 


8 


10 


13 


13 


12 


11 


8 


7 


5 


4 


2 


2 


2 


3 


4 


60 


19 


4 


6 


7 


7 


7 


8 


8 


9 


10 


12 


14 


18 


21 


25 


28 


30 


32 


34 


35 


36 


36 


36 


36 


36 


20.6 


20 


36 


36 


36 


36 


36 


36 


36 


36 


36 


36 


37 


36 


36 


34 


34 


i2 


32 


32 


32 


32 


32 


32 


32 


32 


34.4 


21 


32 


32 


32 


32 


32 


31 


30 


30 


31 


32 


32 


32 


32 


33 


33 


32 


32 


32 


32 


31 


31 


31 


30 


30 


31.5 


22 


31 


32 


32 


32 


34 


34 


34 


34 


33 


34 


34 


32 


32 


32 


32 


31 


30 


28 


28 


28 


28 


28 


28 


28 


31.2 


23 


28 


27 


26 


26 


26 


26 


26 


26 


27 


28 


28 


28 


28 


28 


26 


25 


22 


20 


17 


14 


11 


10 


10 


10 


22.6 


24 


6 


5 


4 


3 


1 





-1 


-1 





2 


4 


5 


5 


5 


5 


2 


-1 


-3 


-4 


-5 


-6 


-6 


-6 


-6 


03 


25 


-7 


-7 


-7 


-7 


-7 


-6 


-6 


-5 


-4 


-1 


2 


4 


7 


8 


7 


6 


6 


6 


5 


4 


4 


4 


4 


4 


0.6 


26 


4 


4 


4 


4 


5 


6 


6 


7 


8 


10 


10 


11 


12 


12 


14 


13 


11 


10 


9 


8 


9 


9 


7 


6 


8.3 


27 


6 


6 


6 


5 


4 


4 


3 








3 


6 


9 


10 


10 


10 


10 


8 


5 


3 


2 


1 








1 


4.7 


28 


3 


4 


4 


4 


4 


4 


4 


3 


5 


7 


10 


12 


14 


15 


17 


17 


15 


12 


9 


6 


5 


4 


5 


4 


7.8 


29 


4 


6 


6 


5 


5 


6 


6 


7 


10 


15 


17 


18 


20 


21 


21 


19 


16 


11 


12 


7 


1 


-1 


-2 


-2 


9.5 


30 


-2 


-2 


-1 


3 


5 


7 


9 


12 


17 


22 


25 


26 


28 


29 


27 


26 


26 


27 


27 


27 


28 


27 


26 


26 


18.5 


31 


25 
14.2 


25 

14.3 


24 
14.2 


25 
14.2 


26 
14.1 


26 
14 3 


26 
14.2 


28 
14,5 


28 
15.3 


28 
17.1 


28 
18 1 


28 
19.7 


27 


25 
20.7 


24 
20 6 


22 
19.9 


22 

18 8 


20 
18.1 


20 

17 5 


18 
16.5 


17 
16.0 


16 

15.4 


16 
15.1 


16 
14 5 


23.3 


Mean 


20.4 


16 6 



30 

AIB TENDS TO EXPAND WHEN HEATED, AND TO YIELD TO PRESSURE WHEN COOLED 

53. Why does air expand when heated? The particles of air are believed to be in 
rapid motion, vibrating in some way back and forth. The faster the vibration, the hot- 
ter the air. The particles are of course too small to see with the most powerful micro- 
scope; the distances through which they move are also very small, and the speed of the 
motion is very great, even for bodies at ordinary temperatures. This is our general con- 
ception of warm bodies. If the vibrations are more rapid when the air is warmer, to 
heat a mass of air is to set its particles vibrating faster, but it is also natural, therefore, 
to think of these particles as pounding on the walls that confine them, and pushing them 
outward, if not resisted by a force too great. Similarly when air is cooled, its particles 
are thought of as vibrating more slowly, and moving through smaller spaces. They may 



HOURLY TEMPERATURES AT HAVANA, CUBA 

JANUARY, 1904 



1 MORNING 


AFTERNOON 




Jan. 


1 1 2| 3 \ 4| 5| 6| 7| 81 9|10|11| N 


1 


1 2 1 3 1 4 1 5 1 6 1 7 1 8 


9 1 10 1 11 1 Mt. 


Mean 


1 


64 


64 


63 


63 


63 


63 


62 


64 


67 


68 


70 


72 


73 


73 


73 


73 


72 


76 


69 


68 


67 


66 


65 


65 


67.4 


2 


64 


64 


63 


63 


63 


61 


61 


66 


70 


73 


75 


76 


76 


76 


77 


76 


74 


72 


71 


70 


69 


68. 


67 


66 


69.2 


3 


64 


64 


64 


63 


62 


63 


64 


68 


73 


76 


78 


76 


76 


75 


75 


75 


75 


74 


74 


74 


72 


72 


72 


71 


70 8 


4 


71 


71 


70 


70 


70 


70 


71 


70 


71 


71 


71 


72 


72 


73 


73 


74 


72 


71 


71 


71 


71 


70 


69 


69 


71.0 


5 


70 


70 


70 


69 


68 


67 


67 


67 


68 


69 


70 


70 


70 


68 


67 


67 


67 


66 


65 


66 


66 


67 


66 


66 


67.8 


6 


65 


65 


66 


68 


68 


67 


67 


65 


68 


73 


74 


73 


73 


73 


73 


73 


72 


70 


68 


67 


66 


65 


64 


64. 


68.6 


7 


63 


62 


62 


62 


61 


61 


61 


63 


67 


71 


72 


73 


74 


76 


77 


75 


74 


74 


73 


70 


69 


67 


67 


67 


68.4 


8 


67 


71 


71 


72 


72 


72 


71 


70 


70 


71 


71 


72 


69 


70 


70 


70 


70 


68 


68 


67 


67 


67 


66 


67 


69.5 


9 


66 


66 


65 


65 


64 


64 


64 


64 


66 


69 


70 


70 


72 


71 


70 


71 


70 


68 


67 


65 


64 


62 


61 


60 


66.4 


10 


60 


60 


60 


58 


57 


57 


58 


60 


64 


70 


73 


74 


75 


78 


77 


77 


77 


75 


74 


70 


70 


70 


70 


70 


68.1 


11 


68 


68 


69 


68 


68 


68 


68 


68 


72 


75 


77 


79 


81 


77 


78 


80 


79 


77 


■74 


72 


71 


71 


71 


70 


72.9 


12 


70 


70 


69 


69 


69 


67 


67 


70 


74 


78 


80 


80 


79 


79 


78 


77 


77 


76 


74 


72 


71 


70 


69 


68 


73.0 


13 


67 


66 


65 


66 


65 


65 


65 


66 


68 


74 


76 


77 


78 


78 


78 


78 


77 


77 


74 


72 


71 


69 


69 


69 


71.2 


14 


69 


67 


66 


66 


66 


66 


66 


66 


67 


69 


68 


67 


66 


66 


65 


65 


64 


64 


63 


63 


62 


61 


61 


60 


65.1 


15 


60 


61 


61 


60 


61 


61 


61 


65 


66 


67 


68 


68 


69 


70 


70 


69 


69 


68 


66 


65 


64 


63 


60 


60 


64.7 


16 


59 


60 


60 


60 


60 


60 


61 


63 


67 


70 


70 


71 


73 


73 


74 


74 


74 


72 


69 


68 


67 


66 


65 


64 


66.8 


17 


64 


64 


64 


63 


62 


62 


61 


62 


66 


73 


74 


73 


73 


74 


75 


74 


74 


73 


72 


71 


70 


68 


66 


65 


68.5 


18 


64 


63 


62 


61 


60 


60 


60 


63 


66 


71 


70 


73 


74 


74 


74 


74 


74 


72 


71 


71 


72 


71 


70 


68 


68 3 


19 


68 


67 


68 


68 


69 


69 


69 


71 


71 


74 


75 


74 


74 


74 


73 


73 


73 


72 


71 


71 


72 


70 


71 


70 


71 1 


20 


67 


68 


70 


69 


68 


67 


68 


68 


69 


72 


73 


74 


74 


75 


75 


74 


74 


72 


71 


70 


70 


69 


69 


68 


70 6 


21 


66 


65 


65 


66 


65 


63 


63 


64 


68 


71 


74 


76 


76 


78 


78 


78 


79 


78 


75 


74 


74 


71 


71 


68 


71.1 


22 


67 


67 


68 


66 


67 


66 


65 


70 


73 


74 


75 


78 


79 


80 


81 


80 


79 


77 


76 


75 


74 


74 


73 


74 


73.3 


23 


74 


73 


72 


71 


71 


71 


70 


71 


71 


71 


73 


75 


78 


79 


80 


80 


79 


78 


77 


76 


75 


74 


74 


73 


74 4 


24 


73 


73 


72 


72 


70 


70 


68 


66 


63 


64 


64 


64 


65 


63 


63 


62 


65 


63 


64 


65 


65 


66 


66 


66 


66 3 


25 


66 


67 


66 


66 


67 


69 


68 


68 


69 


70 


73 


74 


76 


76 


77 


77 


77 


76 


74 


74 


73 


72 


71 


70 


71.5 


26 


69 


69 


69 


69 


69 


68 


67 


70 


71 


74 


75 


79 


80 


78 


76 


73 


73 


72 


72 


70 


70 


70 


70 


69 


71 8 


27 


69 


69 


68 


67 


67 


66 


65 


66 


68 


74 


77 


76 


77 


77 


77 


76 


76 


77 


76 


75 


74 


72 


71 


71 


72.1 


28 


70 


68 


67 


68 


67 


67 


67 


68 


69 


73 


74 


76 


78 


79 


78 


79 


78 


77 


75 


74 


73 


71 


71 


71 


72 4 


29 


70 


70 


69 


68 


68 


66 


66 


69 


72 


76 


78 


79 


82 


84 


84 


83 


82 


79 


76 


75 


74 


73 


73 


71 


74.4 


30 


71 


71 


71 


70 


70 


69 


69 


70 


71 


71 


72 


73 


73 


73 


74 


74 


73 


73 


73 


73 


71 


72 


72 


72 


71.7 


31 


72 
67.2 


71 
67.C 


69 
66.7 


68 
66.4 


68 
66C 


67 
65.6 


66 
65.4 


66 
66.6 


71 
68.9 


76 
71.9 


77 
73.1 


79 
74.0 


80 


82 

74.9 


83 
75.0 


83 
74./' 


82 
74.2 


80 
72.9 


77 
71.6 


74 
70.6 


73 
69.8 


72 

69.0 


71 
68.4 


71 

67.9 


74 1 


Mean 


74.7 


70 1 



31 

be supposed, therefore, to strike less vigorously against the side of the containing ves- 
sel. If under pressure, it is inteUigible that such air should yield to the pressure and 
contract. Much confusion in the theory of the winds arises from the loose doctrine that 
warmed air rises and cooled air sinks. A good test between this and the view stated at 
the head of this paragraph is to isolate some air, warm it and cool it and note its be- 
havior. 

EXERCISE 6 

54. Apparatus: A flask fitted with a rubber stopper, having a single hole through 
which a long glass tube is fitted, and a glass of water. 

Invert the flask, allowing the end of the tube to dip into the water. Note the level 
of the water in the glass and in the tube. Now warm the flask with both hands; note 
and record what happens. What would have happened had there been no outlet? Car- 
rying the apparatus out of doors or to the open window causes what to happen? What 
would have happened had there been no outlet? Drawings should be made of the appar- 
atus, showing the stand of water in glass and tube in all three stages of the experiment. 
What is your opinion of the sufficiency of the statement that warm air rises? Did it in 
this case? That cold air sinks? Did it? If warm air rises, why is not the upper air 
warmer than the lower? Is it? 

WHERE AIR EXPANDS UNDER PRESSURE AND DOES WORK, IT LOSES HEAT 

5.'). Two 500 cubic centimeter fl isks are each fitted with a thermometer to record 
temperature, the first tightly stoppered and the second connected by a U tube containing 
mercury. A scale mounted by a U tube serves to register any variation in the height 
of the ijiercury. The heat is very satisfactorily furnished by two candles of the same 
size. Be careful in setting up apparatus to get all connections air-tight, and that the 
candles are of the same size and mounted with the flame the same distance under the 
flasks (not less than four inches). After the appai'atus has been carefully set up take 
the temperature, light the candles, and record the temperatures in the two flasks every 
minute, also the height of the mercury in the U tube. Record it until no further varia- 
tion in the height of the mercury occurs. Tabulate- your results. Explain any difference 
in the temperatures noted in the two flasks. Suppose we could apply the heat from the 
combustion of a unit of fuel to warm a quart of air enclosed in a glass flask with a rub- 
ber stopper and tube dipping into mercury, as in the experiment. Let us further sup- 
pose that no heat is lost, that the air expands with the heat, pushing the mercury down 
in the tube, and also becomes one degree warmer. Now if the experiment could be re- 
peated with all the quantities and conditions the same, except that the quart of air was 
contained in a strong vessel that would not let it expand, the result would be that the 
air would rise in temperature more than one degree, although its original temperature 
was tlie same, the initial quantity of air the same, the original pressure the same, and 
the amount of heat used the same. The result may be stated thus: the amount of heat 
that somewhat warms air that is free to expand, will produce a greater rise in tempera- 
ture in the same quantity of air confined. If less warming is produced upon air that ex- 
pands, what becomes of the rest of the heat in this case? The answer is that it is used 
up in the work done. When the air in tiie flask expanded, it had to push the mercury 
up in the tube, and that was work. To do work energy is needed. The only energy at 
hand to do the work was the heat supplied, and whatever energy was devoted to expan- 
sion could not also appear as a rise in temperature. 



32 

AIR IS COOLED BY EXPANSION 

56. Now if the flask of air that was closed by the mercury in the U tube could be 
placed under the receiver of an air pump and some of the air pumped out of the receiver 
the air within the flask would expand, would push down the mercury in the near side 
of the tube and up, of course, in the other. This would be doing work, but we are not 
now supplying heat to do this work with. If the temperature of the air in the flask were 
noted before and after the experiment, what should we see? Energy that was just now 
occupied in what we might call heat work — moving the air particles back and forth at 
the rate proper for the temperature — has now been diverted to lift a little mercury 
against gravity. Only a part of it, therefore, is now engaged in heat work, or, we may 
say, the air has been cooled in expanding against pressure. If a quantity of air is com- 
pressed into a strong vessel and allowed to stand until it has taken the temperature of 
the room, it will suffer a distinct fall of temperature if allowed to expand under pressure 
as in the previous experiment. In this case it has only its own heat to call on to do the 
work of expansion, and as soon as that is done the temperature falls. It appears, there- 
fore, that not only does heat cause expansion, but that expansion taking place, as it 
usually does, against pressure, uses up heat and causes cooling. This must not be taken 
to mean that expanding air always falls preceptibly in temperature, the fall is only^pre- 
ceptible when no external heat is supphed to it, or not enough to do the work. When 
external heat is supplied, the temperature rises all the time the air expands. In thought 
only do we have a succession of events; first, the air warmed x plus y degrees; second, 
the air, expanding, uses up some of its heat and cools through y degrees, with the final 
result of a rise in temperature of x degrees and an increase in volume. In reality heat- 
ing and expansion are simultaneous. Some of the heat is applied to the heating, while 
the rest is used in expansion. 

For the air that was not allowed to expand, all the energy supplied was applied to 
raising the temperature, which accordingly rose higher than that of the expanding air. 

AIR IS WARMED BY COMPRESSION 

57. On the other hand when air is compressed by the application of force, the en- 
ergy used is transformed into heat and the air warmed. When gases are mechanically 
compressed, provision has to be made by the circulation of cold water or otherwise, to 
get rid of the heat generated. (Tyndall's "Heat as a Mode of Motion," lectures I and 
III, may be read in this connection.) 

GEOGRAPHIC APPLICATIONS 

58. All of the layers of air in which the phenom.ena of the weather take place, are 
under pressure from the atmosphere above. If this pressure diminishes, the air expands, 
and is thereby cooled. Conversely when the pressure increases, the air is compressed 
and warmed. As the winds move over the surface of the earth, at times they ascend 
and descend the slopes of the mountains. When they ascend they go nearer the surface 
of the ocean of air. In that case there is less air above them, so they are able to expand 
and lift the air above, which cools the winds because of the work done. In general, AIR 
THAT RISES EXPANDS AND COOLS. When the winds descend they go deeper below 
the surface of the ocean of air. As this puts more and more air above them, they yield 
to the increasing pressure, contract, and are warmed by this compression. In general, 
again, AIR THAT SINKS IS COMPRESSED AND WARMED. 



33 

59. Since the pressure of the atmosphere at various levels is pretty well known, 
it is possible to calculate these changes of temperature due to ascent and descent 
of air. They amount to 5.2" per thousand feet and are known as adiabatic tempera- 
ture changes. They apply only to AIR that rises and falls. A person climbing a thous- 
and feet up on the side of a mountain would not find it 5.2° cooler above unless the 
air went up with him. It often occurs to students at this point that these doctrines 
are contradictory. Descending air is compressed and warmed, but since warmth causes 
air to expand, it may seem as if the work of compression would be at once undone by 
the action of the heat generated. The diff],culty is apparent only. Heat does not cause 
expansion but a tendency to expand. Whether a gas expands or not depends on the 
pressure to which it is subjected. To say that descending air is compressed is to say 
that it has not enough expansive energy, EVEN WITH WHAT IS ADDED TO IT BY 
THE HEAT OF COMPRESSION, to enable it to resist the pressure of the air above. 

It is often taught that cold, lofty mountains cool the warm winds that blow on them 
from oceans and thus make them drop their moisture as rain. We have seen that the 
cooling is really adiabatic cooling within the air itself and therefore not caused by the 
mountains. The doctrine referred to makes us wonder what keeps such mountain tops 
cool, for, since the air is constantly flowing over the mountains today, tomorrow, next 
year, next century and for thousands and thousands of years it is evident that such 
enormous volumes of warm air must rather warm the mountain than be cooled by it, 
for the hugest chain is of insignificant bulk beside such masses of air as that. 



60. Master and memorize the following argument. 

The wind is moving lower air 
When: 

wind comes to a mountain, wind goes by a mountain top, 

1 The mountain sends it up. 1 The earth pulls it down. 

2 The wind has less air above. 2 The wind has more air above. 

3 The wind expands and lifts air above. 3 The air above settles down on the wind 

and compresses it. 

4 This work cools the wind. 4 This work warms the wind. 

5 This cooling forms clouds. 5 This warming dissolves clouds. 

THE UNITED STATES WEATHER BUREAU 

61. Every morning observations are taken of thermometers, wind vanes and other 
instruments at some ninety stations in various parts of the United States. The results, 
together with some contributed from neighboring countries, are combined by telegraph 
to make a daily forecast of the weather. The total cost of the service of the Weather 
Bureau to the nation is near a million and a half dollars a year. Wliat do the people get 



34 

for their money? Not certain forewarning of every rain. That the Weather Bureau 
cannot give. What we do get from the Weather Bureau, however, is worth many times 
the appropriation every year. It is a service in three forms: (1) The saving of hfe and 
property in ships on the seas and Ial?:es by warning the people of dangerous storms, (2) 
the saving of life and property along great rivers by warning the people of dangerous 
floods, and (3) the .saving of perishable foods, growing or in transit, by warning the 
people of severe frosts. Vessels in port, on the great lakes or oceans, are warned by the 
Weather Bureau of every serious storm that is liable to affect them. There are prac- 
tically no failures in these warnings. The slighter changes in the weather cannot be 
predicted with certainty, but the great ones that endanger life can be foretold with 
great accuracy, and none of them now take us unawares. Almost equally great is the 
saving accomplished by the river service, notably in the Ohio and Mississippi valleys 
where many people live. No dangerous rise in these rivers but is foretold by the Weath- 
er Bureau in time for dwellers on the lowlands to escape to the higher land and carry 
movable property beyond the reach of flood. Even the probable hour and height of flood 
at various points is pretty well announced beforehand. A recent illustration was the 
Ohio flood of February 19, 1908. So many perishable foodstuff's, largely fruit an^ veg- 
etables, are now constantly in transit across the country, so many grow in regions like 
California and Florida, liable to be visited by destructive frosts, that forewarning of all 
cold waves makes possible great saving of property by protecting growing crops from 
frost, and warming or affording other artificial protection to those in transit. Refer- 
ence might be made to the frost of January 20, 1908, in Florida. Shippers of such goods 
now rarely fail to enquire of the Weather Bureau about the temperature conditions to 
be expected during the time of an important shipment. There is certainly no depart- 
ment of the national government that gives a handsomer return on an investment of 
the people's money. 



EXERCISE — Dra« iiiis Isotlicrms 

62. We shall best familiarize ourselves with the details of the daily weather map 
if we practice some parts at least of its construction. To this end we will use data tele- 
graphed to Washington to construct a map of isotherms. 

Isotherms are lines drawn through places having the same temperature. They are 
commonly drawn at intervals of 10° through places having temperatures evenly divisible 
by ten, as 0°, 10°, 20°, 30°, etc. Usually the temperatures given are either higher or 
lower than the desired temperature. In such cases do not merely draw the isotherm be- 
tween the" two places, one of which has a higher and one a lower temperature than the 
temperature desired, but make an exact estimate each time. We have 27° and 35° for 
instance and wish to place the isotherm of 30° in that neighborhood. We should place 
a point f of the distance from the place having a temperature of 27" to the one having 
a temperature of 35° and through that point draw the isotherm. 

Making use of the above principle in drawing isothermal lines, draw the isotherms 
for one of the days, the data for which are given below: 



35 



Kleva- 

tioD in 

(eel 



Tempera- 
ture 



Kleva- 

tion io 

feet. 



Tempkra- 

TURE 



Father Point 

Chalbam 

Halilax 

Quebec 

Montreal 

Albany 

Boston 

New Yurk 

Parry Sound 

Buffalo 

Oswego 

Binghamton 

Philadelphia 

Washington 

Norfolk 

Charleston 

Sault Ste. Marie 

Alpena 

Saugeen 

Detroit 

Toledo '.. 

Erie 

Cleveland 

Cincinnati ..;.. .. 

Knoxville 

Jacksonville 

Tampa 

Key Vt est 

White River 

Port Arthur 

Marquette 

Escanaba 

Oreen Bay 

Milwaukee :... 

Chicago 

Louisville 

Cairo 

Chattanooga 

Memphis 



100 

100 

227 

293 

60 

97 

125 

314 

600 

768 

335 

123 

117 

112 

57 

48 

6i4 

609 

656 

730 

674 

714 

762 

628 

1004 

43 

36 

22 

1147 

608 

734 

612 

617 

671 

824 

525 

359 

762 

399 



30 40 
.40 
.38 
.42 
.42 
.43 
.44 
.43 
.30 
,39 
.42 
.42 
.42 
.41 
.41 

24 
.17 

23 
.32 
.30 
.28 
.36 

32 
.25 
.24 
.18 
.15 
.14 
.08 

05 
.13 
.17 
.16 
.28 
.18 
.22 
.13 
.21 
.05 



30 03 

"".00 
29.64 
.55 
.66 
.67 
.73 
.67 
.75 
70 



.77 

.83 
.87 
.96 
.86 
.79 
.73 
.86 
.90 
.80 
29.88 
30.01 



29.98 



30.01 
03 
.12 

30.02 



29.97 
29.97 
30 01 
30.05 
.01 
.05 



-7 
-13 
20 
-4 
-1 
7 
9 
13 
10 
12 
7 
8 
20 
20 
26 
40 
21 
17 
10 
20 
22 
15 
IS 
28 
33 
46 
50 
63 
22 
17 
20 
20 
23 
28 
30 
31 
36 
37 
33 



43 



50 
50 
56 
62 
62 
66 
49 
59 
59 



68 
71 
73 

It 
50 
49 
60 
61 
61 
64 
64 



75 



78 
37 
36 
39 



56 
58 
65 
66 
70 
68 



Duluth 

St. Paul 

Lacrosse 

Davenport 

Kansas City 

Fort Smith 

New Orleans 

Galveston 

Minnedosa 

Winnepeg 

Moorhead 

Huron 

Omaha 

Dodge 

Abi'ene 

Qu'Appelle 

Bismarck 

Pierre 

Rapid City 

North Platte 

Denver 

Prince Albert 

Battleford 

Swift Current 

Havre 

Miles City 

Lander 

El Paso 

Calgar) 

Medicine Hat 

Helena 

Modetia 

Kamloops 

Spokane 

Winnemucca 

Los Angeles 

Portland, Ore 

San Francisco... 



702 

837 

720 

599 

963 

481 

54 

54 

1671 

757 

935 

1306 

1103 

2504 

1749 

2134 

1674 

1460 

3251 

2826 

5290 

1398 

1500 

2423 

2494 

2372 

5372 

3767 

2263 

2171 

4108 

5000 

1160 

1943 

4340 

330 

153 

153 



30.02 
29.96 
30.03 
30 04 
29.98 

29 86 
30.02 
29.87 

30 12 
.12 

30 12 

29 89 
29.85 
29.69 
29.77 

30 09 
30.12 
29.95 
30.01 

29 84 
29.95 
30.27 

.31 
.30 
.30 
.10 
.13 
.00 
.35 
.33 
22 
.31 
.31 
.40 
.36 
,2? 
.20 

30 29 



.17 
.15 

.08 
06 
.13 
.06 
.03 
.01 
.43 
.43 
.32 
.34 
.20 
30 08 

29 98 
30.34 

.44 
.40 
.38 
24 

30 17 
30.27 

.24 

.27 

.25 

.36 

30.20 

29.88 

30.13 

.23 

30.18 

29.88 

29 98 
30.11 
29.99 

30 02 
30.00 
30.03 



28 
31 
31 
32 
33 
38 
48 
53 
00 
10 
23 
20 
30 
30 
51 
11 
15 
22 
22 
26 
26 
6 
7 

15 
21 
21 
20 
40 
8 
15 
25 
19 
17 
31 
18 
43 
37 
42 



40 
48 
53 
60 
63 
71 
75 
76 
41 
41 
44 
48 
56 
64 
73 
40 
43 
48 
48 
55 
56 
41 
43 
43 
44 
45 
50 
72 
48 
46 
47 
49 
60 
50 
51 
57 
60 
58 



SURFACE ISOTHEKMALS, AND 




l''is. 14. Normal Surface Tempciruture for .liiiiu 



SEA LEVEL ISOTHERMALS 

63. If all the temperatures for the 
month of June for many years are av- 
eraged and represented by isothermal 
lines, the result is CLIMATIC and 
shows the distribution of temperature 
usual at that season. Such a map is the 
accompanying Figure 14, showing nor- 
mal surface temperatures for the 
month. It is supposed to show the 
temperatures to be expected at any 
place in the country at any time. It 
fails to do so however, at present, be- 
cause the number of points of observa- 
tion is entirely too small. Some sta- 
tions are high and therefore, cooler 



36 



than neighboring places, others in valleys are warmer than the country around. Iso- 
therms drawn from such data cannot expect to represent the country correctly. Thus 
two valley stations in the mountains might each have a temperature of 30 degrees. But 
the isotherm drawn from one to the other might very likely pass across a mountain 
range several thousand feet above. The temperature up there may be nearly zero, yet 
the map reports it as 30 degrees. Any such map has this defect unless the observation 
stations are numerous enough to represent the actual topography, which is never the 
case. The difficulty is met by "Reduction to Sea Level." The air is known to be cooler 
and cooler as one ascends above the level of the sea. From kite and balloon studies and 
others along the slopes of mountains, it is seen that the temperatures of high places are 
lower than they would be if the ground were lower. A series of corrections has been 
prepared by which temperatures at all heights are reduced to the level of the sea. The 
United States Weather Bureau adopts the following values: — 



December to February - - - - 
March to May and September to November 
June to August ----- 



1.5 degrees per 1000 ft. 
2.0 degrees per 1000 ft. 
2.5 degrees per 1000 ft. 



Thus a place 5000 feet above sea level has a normal surface temperature for June 
of 62.5°. The reduction to sea level for that time and height is 5 times 2.5° or 12.5". 
The corresponding sea level temperature is 75 '. If all the values are so reduced fo sea 
level, and a system of isotherms drawn with the resulting numbers we shall obtain the 

distribution of tem- 
peratures about as 
they would be if the 
whole surface of the 
country could be 
smoothed down to 
the level of the sea. 
Fig. 15 is such a map 
of sea level isotherms 
for June. Though it 
does not correspond 
to any actual condi- 
tions, it does enable 
us to learn the nor- 
mal surface tempera- 
ture at any point and 
any elevation. Thus 
the sea level June 
normal for Toledo is 
70°, the elevation 674 
feet. Subtracting 
shown in Figure 14. 
What is the June 




Figure 15. ,Sea level iioriiials for Juiie 



Vs of 2.5°, or 1.6°, we have a surface normal of 68.4°, about as 
Pikes Peak is at latitude 39°, longitude 105°. It is 14,000 feet high, 
temperature up there? 



EXERCISE 9— SpeHs of Weather 

64. Construct temperature curves for January, for both Ypsilanti and Havana, 
using the mean temperatures of the days as given in the right-hand columns of tables 



il-I 



-m 



7Q 



-u 




56 



1 ^ 



37 

at pages 29 and 30, calling each square of quadrille paper one degree vertically and hori- 
zontally one day. Both curves may be placed on one diagram by numbering the top line 
74, the bottom 0,. and omitting 36 to 64. 1. Does any diurnal sun effect show in this 
curve? 2. Does either curve show that the air got steadily wanner or colder through 
the month? 3. Which curve shows the more distinct spells of weather? 4. How 
many warm spells at Ypsilanti? 5. How many cold? 6. How many days did that 
make a spell last on an average? These spells are the special characteristic of 
our weather except, usually, in May, June, July, and August. Now construct diurnal 
curves for both places with the mean hourly temperatures from the bottom of the tables. 
Put them on the same diagram, using the same temperature scale but calling one square 
horizontally one hour. This enables us to compare the diurnal temperature ranges with 
what we might call the spell ranges, the difference between the cold spells or the warm 
ones that follow or precede. 7. At which place is the spell range greater than the diur- 
nal? 8. How many times as great? This, too, is characteristic, a feature of the cli- 
mates of these places. At the one place temperature changes are mostly from daylight 
warmth to nightly cooling, at the other this signifies much less than change from warm 
spell to cold and back. At one of the places days may be even colder than nights, as on 
January 7 and 11. 

EXERCISE 10 

65. Figure 16 shows the maximum and minimum temperatures observed at Ancon, 
Panama canal zone, and Detroit, Michigan, every day from October 1, 1912, to October 
31, 1913. 1. How many distinct cold spells, of at least three days' duration, can yai 
count at Ancon? 2. How many at Detroit? 3. What is the greatest peculiarity of the 
year's temperatures in the canal zone? 4. How did Detroit's temperatures in its hot- 
test month differ from those of Ancon? 5. Did Detroit ever have a whole month of 
Tropical temperatures? 6. A whole week? There were 15 occasions when it was hotter 
at Detroit than at Ancon. 7. Which of these dates can you make out on the diagram? 
8. Which place has the greater daily range of temperature? 9. In what month does 
each place have the least range of temperature? It is caused by clouds each time. 

This exercise should help you to see that the "Torrid" zone is not so much a hot zone 
as a zone that is steadily warm and especially that it has nothing corresponding to our 
winter. In the year studied both places happened to have the same maximum tempera- 
ture of 96°. But Detroit has known a maximum of 104° and Ancon's highest (in a rec- 
ord of only 8 years) is only 97°. Further our "Temperate" zone temperatures are not 
temperate at all but characterized by violent changes, as in March when one week saw 
the temperature jump from 3° to 67°. It is the zone of spells of weather. 

IRREGULARITY OF TEMPERATURE DISTRIBUTION IN LONGITUDE 

66. From the isothermal map it appears that places on the same parallel of latitude 
have different tempei-atures. This is not only due to different elevations above the sea, 
but also because the sun's rays fall on surfaces so different even where the rays have 
the !>ame inclination. Land and water do not heat up equally under the sun, nor do bare 
.and grass-covered lands. The red and yellow desert of North Africa, the blue Atlantic, 
and the plant-covered land bordering the Gulf, do not undergo equal heating, so it is 
not strange that the air above them has varying temperatures. A continent or large 
island, like Australia, Madagascar, New Zealand, or Great Britain is always warmer 



November 



Decetnbe 



Jar\vary_ 



Fe brudTt) 



March 



April-I 




Figure 16. A year's actual temperatures at Detroit and Ancon 



38 

than the neighboring sea in summer and also cooler in winter; for the land not only 
heats up more under the sun's rays, but also cools off faster in winter. 

Seasonally .and with the spells of weather that succeed each other in our latitudes 
very great differences in temperature result from the importation of southern and 
northern air on the wind. Spring Is due with us, for instance, when the sun reaches 
a certain elevation in the sky; it is apt to come with a week of south wind. This is 
especially true in the region of the Great Lakes where the south wind is needed to melt 
the ice sheets in the large bays. 

PRESSURE 

67. It has been pointed out that we live at the bottom of the ocean of air just as 
the inhabitants of the sea bottom pass their lives at the bottom of the ocean of water. 
But the gaseous nature of our atmospheric ocean gives it great peculiarities. A shell fish 
in deep water has always the same amount of water above him, .and about him it is 
always still. There are tiny changes in the quantity of water as waves pass above, and 
there are slow movements of sidewise drifts and currents. Entirely insignificant, how- 
ever, both of these in comparison with wliat occurs in the air. We have very great 
differences in the amount of .air above us and it moves about on the earth's surface 
with the high velocity of the storm winds. Some knowledge of the varying amount of 
air above is necessary to understand the winds. It is not possible to feel it directly; its 
manifestation is in that somewhat vague thing called air pressure, and the instrument 
that shows it, the barometer. It is so grounded, however, on changes of temperature 
that we may form an idea of it very readily by noting temperature changes. Paragraph 
68 will help the student see what a barometer is and how air pressure is only a vague 
name for the quantity of air over the spot being studied. 

We shall now regard the rising of the barometer as indicating that more air is 
coming to the region, its falling as signifying less air present, i. e., some air 
is going away. 

BALANCING COLUMNS, WATER AND MERCURY 

68. Materials: 2 glass jars, 18 inches high, and 3 and 1^ inches wide, respectively; 
1 g''ass tube, 36 inches long, -J inch wide; 1 pound of mercury. 

Put some mercury in the bottom of the smaller jar, stand the glass tube in the mer- 
cury, and pour water upon the mercury in the jar until the water is 13 inches deep. 
Note what happens within the glass tube. Make a measurement of height ?ibove mer- 
cury in jar. If the water is now withdrawn with a siphon, notice what happens within 
the tube as the water level falls in the jar. In siphoning, the water should be run into 
an empty jar, so that if any mercury comes over it may not be lost. If the water in the 
service pipe contains lime or other salts, distilled water should be used. 

Repeat the experiment in the larger jar. When you have a column of water 13 
inches deep over the mercury in this jar, how does it compare in bulk and weight with 
the water in the first experiment? Suppose we had a jar a foot wide, and put water in 
it 13 inches deep over mercury in which a tube had been previously placed, what would 
happen within the tube? 

Suppose a bowl of mercury with a tube standing in it were placed in a pond or tank, 
so that the mercury was just 13 inches under the water surface, while the tube project- 
ed above the water surface, what would happen? 

What one quantitative condition must always be fulfilled in these experiments to 



39 

get a column of mercury to balance a 13-inch column of water? To balance any column 
of water? 

In all these cases both fluids have been visible, but once we know the principle, tlie 
water might be concealed, and we could still judge of its height vei'y accurately by the 
height of the mercury in the tube. 

We might in the same way balance a column of gas against the mercury. Thus the 
heavy violet vapors of iodine weigh , Jo^; as much as mercury. How long a tulje filled 
with iodine vapor would balance one inch of mercury? How many inches? How many 
feet? In the calculation we might disregard the compression in the bottom of the col- 
umn by the weight of the vapor above. That would require a long tube, indeed, but it 
would be conceivable. Although it would be balancing gas against liquid, both would 
still be visible on account of the violet color of the gas. But as long as the mercury is 
visible, the same balance might be made with a colorless gas like air. Air under stand- 
ard conditions weighs moi, as much as mercury. How many inches, feet, and miles 
of ail' in a column would balance an itich of mercury? 

A barometer is really a tube in which a column of mercury balances the atmos- 
phere of air. By the height of the mercury column we judge the height the air colunm 
would have if it were of uniform density and composition throughout. The mercury in 
the barometer at sea level stands about 30 inches high. How high a column of homo- 
geneous air, equally dense from top to bottom, would that represent in miles? 

We have thought of a bowl of mercury in which a tube is placed and the whole 
lowered into the pond. As long as the tube projects above water, its walls keep the 
mercury within from experiencing the pressure or weight of the column of water that 
rests on the mercury in the bowl without. As for the atmosphere in these experiments, 
it presses on the mercury inside the tube and on the water without alike, so it is just 
the same as if it exerted no pressure at all. 

Now, our thought of the atmosphere is of a widespread layer of air resting upon 
the earth, thin or rare above, where the high mountains reach up into it, thicker or den- 
ser below, where the weight of the upper layers that rest upon it presses it together. 
There is probably air a hundred miles above the surface of the earth, yet remembering 
that the earth is 8000 miles through, while vastly the greater part of the whole atmos- 
phere is compressed into the lower ten miles, we see that it is a relatively thin film, fair- 
ly comparable to the skin of an apple. Let us now try to imagine a bowl of mercury 
with its tube set into this ocean of air just as we thought of another set into a pond. 
The tube must always be thought of as long enough to reach up through the whole thick- 
ness of the atmosphere. Thus there will be no air within the tube, it being kept out by 
the glass walls. The mercury rises within the tube to balance the weight of air with- 
out on the surface of the mercury in the bowl. The hundred-mile-long tube would not 
be needed. If its waLs could be fused together a few inches above the top of the mer- 
cury in the tube so as to keep the air out, the balancing would go on just the same. 
If more air came to that neighborhood, as in the crest of a wave, the colunm of mer- 
cury within the tube must rise to balance it. That is essentially what a barometer is, 
and how it works. 

69. That "the air presses" is believed to be an easier conception for beginners than 
the "pressure of air." As a form of words both may mean the same thing, but only 
one reality, the air, is involved, and the first statement may be regarded as the direct 
statement of fact. The pressure, on the other hand, has no real existence except as a 



40 

word. It is not a thing at all. Suppose the result of the action be a broken window. 
It is the air that breaks it and not the pressure. This is just as true as if we were talk- 
ing of a ball flung at a window. The hall really breaks the glass, though we may use a 
variety of other phrases about it, each' of which may have some value of its own; ajs, 
the force of the ball breaks the window, the momentum, etc., the glass was broken by 
the impact of the ball, a boy broke the glass with a wild ball, the blow of the ball upon 
the window broke it. Yet upon examination it appears every time to be the ball that 
breaks the glass. All abstract nouns have the same indirect relation to reality. Thus in 
the sentence, "This man's influence in the community is powerful," the influence is 
the subject of the verb, but the man is the real agent. This appears in the direct state- 
ment, "The man influences the community strongly." "The wife's energy supplemented 
the ability of the husband." "The energetic wife helped the able husband." It is not 
pretended that the direct form is universally preferable. In the last example the first or 
indirect statement is much better. But in cases where quantities enter that are to be 
measured and thought of as acting, there is a great gain for elementary presentation in 
the direct statement and the avoidance of the abstract noun. It is air that afl'ects the 
barometer, and not pressure of the air. If more pressure does not imply more air, it 
means nothing at all. Of course there is no reason why anyone who has once become 
familiar with the instrument should avoid the convenient word. But, though entirely 
justified and in the very best use, it is often a cause of early misunderstanding. 

BAROMETER CORRECTIONS 

70. Unlike the thermometer, the barometer readings need correction before they 
are transferred to the weather map. The corrections are two, for temperature and 
elevation. Since mercury expands with heat, the amount of mercury needed at any mo- 
ment to balance the atmospheric column will measure more or less inches according as 
the instrument is in a cold or warm room. To have a means of comparing the readings 
of different instruments, it is necessary to allow for the temperature by calculating 
what the length of the column of mercury would have been had the temperature been 
that of freezing water. This is called the reduction to freezing point and must be ap- 
plied to all readings of good barometers. 

The reason for the second correction, the reduction to sea level, is that we desire 
to know the distribution of atmospheric pressures at some uniform level. That the 
pressure varies at different levels we know. To understand the winds it is necessary 
to find out whether it is constant at any one level. So the readings are always reduced 
to sea level. 

Read the thermometer and barometer outside the window and those within. Where 
is it colder? How much? Where is the barometer "higher"? How much? Divide the 
difference in barometer readings by the number of degrees difference in temperature to 
ascertain how much the outer barometer seems to have fallen per degree of greater 
cold outside. The published tables of corrections for temperature allow for the expan- 
sion of the mercury, the glass tube, and the brass scale and do NOT apply to a barom- 
eter with a wooden scale such as is used in these experiments. The wood is more affect- 
ed by moisture than heat, but changes with absorbed moisture are too irregular to be 
calculated. 

EXERCISE 11— Drawing Isobars 

71. Isobars are lines drawn through places having the same air pressure. They 



41 

are commonly drawn on weather maps for intervals of one-tenth of an inch through 
places having- pressures ending in even tenths as 30.1, 30.2, 30.3, 30.4, etc. In many 
places where pressures are given they are higher or lower than the desired pressure. 
In such cases do not merely draw the isobar between the two places, one of which has a 
higher and one a lower pressure than the pressure desired, but make an exact estimate 
each time. We have, for example, two places having pressures of 30.10 and 30.30 and 
wish to draw the isobar of 30.20 in that neighborhood. We should locate a point just 
half way between the two places and draw our isobar through that point because 30.20 
must necessarily lie just half way between 30.10 and 30.30. The method is the same 
one used in drawing isotherms. 

On the weather map for January 20, printed in this book, what are the pressures 
at Duluth, Detroit, Buffalo, Chicago, and Winnipeg? What at the same places January 
22? What on May 27? 

RELATION OF AIR TEMPERATURES AND PRESSURES 

72. The system of isobars drawn with the readings for data A shows a grouping 
of low barometers in the central valley, west of the Mississippi, with higher barometer 
readings grouped over the Rockies and again over the Allegheny mountains; for data B 
high barometers on the 100th meridian and low in the St. Lawrence valley. Remember- 
ing that the readings have been reduced to sea level, what thought about the depth of 
the air over various parts of the country would explain such distribution of pressure 
on the supposition that the temperature is the same everywhere? Does that suggest a 
level upper surface of the atmosphere like that of the ocean? Of course our supposition 
is improbable. The temperatures are not the same everywhere. The isothermals show 
differences even on the same parallel of latitude. You have learned from the daily 
weather map, that there is definite association of temperatures with the areas of liigh 
and low barometer. You are, therefore, in a position to judge the sort of error involved 
in our assumption of uniform temperatures all over the country on dates A and B. 
What are the real conditions of temperature in the country that morning? As warm air 
expands and occupies more space, while cold air contracts and occupies less, we must 
modify our previous thought about the depth of air in various places. What shall we 
now -believe about the air surface? 

73. Think of Australia in hot weather. The relation between pressure and tem- 
perature is a causal one. The pressure varies because the heat varies. Suppose the air 
tends to expand and mound up there overhead. 1. Would this make the pressure there 
less? 2. Would it make the air there weigh less? 3. Would the barometers go up or down 
because of this tendency to expand? 4. Why not? 5. Is a bar of iron lighter or heavier 
when hot? 6. Wliy should a mass of air be? 7. Is it true that warm air is light? 8. If 
some air in a bag weighs a pound, will it weigh less when we warm it? The only sense 
in which warming makes it lighter is that it expands and occupies an amount of space 
that would at the lower temperature be occupied by a greater amount and weight of air. 
9. What will happen after the air has expanded and mounded up aloft? 10. If some air 
goes away above how will that affect the barometers lielow over the sea? 11. How in 
Australia? 12. Under such circumstances the winds will lilow in toward Australia from 
all around. This actually happens every summer. Wliy? 13. Would you say such winds 
are caused by temperature or difference of temperature? 14. Whicli is the more imme- 



42 



diate cause, difference of temperature or difference of pressure? 15. What causes the dif- 
ference of pressure? Tlie sun's heat causes a change in the condition of the air. 16. What 
is this change? Motion is involved in this change but it is motion vi'ithin the mass and 
not motion of the mass. The familiar statement that hot air arises is convenient some- 
times, like the statement that the sun rises, but neither is exact. The lower air is always 
much warmer than the air above the earth, but it is usually quite content to stay below 
without any tendency to rise, being so compressed by the weight of the air above that is 
not so light, quart for quart, as it is. Expansion, with motion within the mass, is the only 
direct result of heat. But this expansion gives an opportunity to another force to cause 
motion of the mass. 17. What is this force? 18. Is the first tendency to motion of the 
mass active above or below? It is at this moment that change of pressure appears. The 
pressure of the air is merely a manifestation of its mass and cannot change unless the 
quantity of air changes. If air goes away there will be less air, less weight, and less 
pressure. And wherever more air goes there will be more weight and more pressure. 
The depth of the atmosphere to sea level is to be thought of as fairly constant since an 
excess of depth anywhere at once begins to find a remedy by the action of gravity. 

74. Heat causes a tendency to expand; expansion gives gravity a chance to move 
off air above, this causes unequal pressure within and without the warm area 
in the air below, unequal pressure below sets the lower air moving or causes 
winds. Do the winds then generally move toward places that are cooler or warmer 
than places around? It is familiar that the sun is always high in the sky near the 
equator, causing greater heating there than near the poles. Nearer the poles are alter- 
nate seasons of high sun or summer, and low sun or winter, when the rays more near- 
ly graze the earth's surface and warm it much less. Thus the strip of highest tem- 
perature and lowest pressure migrates across the equator with the sun twice each 
year. We shall presently find winds and rainfall migrating similarly. The mercurial 
barometer should now be read daily and the results recorded in the note book. 

Saturday and Sunday readings may be taken from the barograph sheet posted every 
Monday. " The barograph sliould also be glanced at each day to see whether the' barom- 
eter is at the moment rising or falling, and this fact recorded. 

WINDS 

75. The wind is the lower air moving. The motion is from a region of high pres- 
sure to one of low pressure, and these differences of pressure almost always have their 
cause in differences of temperature. Among the simplest cases are the continental winds 
of Australia, referred to in paragraph 73, and shown in the diagrams (Figs. 17 and 18) . 



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Figure IS. July 



43 




Flgiu'e 19. Average winds oi the Uiii'tcd States, July 




Figure 20. Average wlnnls of the United States, December 



On our shores the actual winds result from composition of the permanent SSW 
winds with landward winds in summer and seaward winds in winter. 



44 

How will the land and sea pressures near Australia compare in December? Such 
seasonal alternations of the winds from the sea and land are called MONSOONS. North 
America has less pronounced but preceptible monsoons. (Figs,. 19 and 20.) They are 
most strongly developed in the northern Indian Ocean. (Figs. 21 and 22.) 2. In what 
season will southern Asia be warmest? 3. When will it have the lowest pressure? 
4. Why does the southern monsoon blow there in summer? 5. Why the northeast mon- 
soon in winter? 6. Which American coast is situated most like the south of India? 
7. Are the winds similar there? 




50 60 70 80 90 100 110 

Fig-ure 21. Wliitei' monsoon, January, February 




50 . 60 70 80 90 100 110 1?0 



Figiu'e 22. Suuiuicr monsoon, July, August 



45 

EXERCISE 12 —Cyclonic Winds 

76. 1. By an inspection of the weather maps (Figs. 23 to 25) for January 20, 21, 
and 22, 1902, what would you decide to be the general movement of the air around areas 
of low pressure — toward or away from the center? 

2. On the map for January 21, 1902, how do the winds seem to be blowing about 
the low pressure area centered over eastern Tennessee? 3. Are they blowing straight 
toward the center? 4. If not, to which side of the center, right or left? This means 
fbr a person facing the center. Look straight north of the area on Lake Erie., 5. If 
the winds there blew straight AT the area they would be north winds. 6. Are they? 
If they go west of south they turn to the right, /. e. to THEIR right of straight ahead. 
7. Do winds at stations straight to west of Tennessee go toward southeast (right) or 
northeast (left)? 8. As you look at the other maps again, does the same thing seem 
on the average to be true? 

State in general terms the movement of the air around the cyclone. Illustrate by a 
diagram, using six arrows to show the direction of the wind, and show to the instructor. 
Make the shaft of each arrow straight and half an inch long. 

EXERCISE 13 — Anticjclonic Winds 

77. Examine the weather maps for May 26, 27, and 28, 1902, and determine 
whether the air around the areas of high pressure seems to be moving outward or to- 
ward the center of the area. 

1. On the map for May 26, do you detect anything besides the outward movement 
of the air? 2. Do the winds blow straight out, to the right of straight out, or to the 
left of straight out? 3. Do you discover any verification of your conclusion on the 
maps for other days? 

State in general terms the movement of the air in the anticyclone. Illustrate by a 
diagram as you did for air movement in the cyclone. 



46 




47 




48 





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52 

LAND AND SEA BREEZES 

78. When the winds shift from day to night instead of from summer to winter, 
they are called land and sea breezes. Like all winds these are named from their point of 
origin. They are observed on most sea shores and on many lakes, being distinct in sum- 
mer on Lakes Huron and Michigan, on days of feeble general circulation of the air. In 
winter the land is usually colder than the lake, even by day, so the lake breeze is absent. 

Lake or sea breezes that blow by day to the heated land are always stronger than 
the land breeze of the night, mostly because the rougher land surface offers more resist- 
ance to the passing of the air than the water does. It is always the case that the wind 
blows faster on the water than on land. For the same reason, kites, balloons, and clouds 
show the movements of the upper air to be much more rapid than the winds below. 
Mountain winds confirm us in this view of the effect of friction in retarding the wind 
at the earth's surface. 

Average wind velocity in miles per hour at various shore and inland stations: 



Block Island 


17.2 


Key West 


10.5 




Boston 


11.8 


Salt Lake City 


6.0 




Chicago 


17.0 


San Francisco 


10.6 




Cincinnati 


7.7 


Woods Hole 


15.8 




Galveston 


10.9 


Denver 


8.0 




Hatteras 


13.9 


Pikes Peak 


18.0 




Kansas City 


8.6 


Mt. Washington 


34.0 


(36.0 in winter) 



THE WINDS OF OBSERVATION 

79. We should gather material for the study of the winds by noting the direction 
and force of the wind each morning with the principal changes during the day. We may 
use the data gathered from a wider area on the daily weather map, and we may note 
the effect of the prevalent wind on the trees. This is often well shown on fruit trees, 
which yield the more readily as the ground is kept soft by cultivation, unless, indeed, 
the farmer has been prudent enough to plant his trees leaning against the wind, as is 
sometimes done. In what direction does this make fhe trees lean with us? Select iso- 
lated trees in the country, to which the wind has free access, and note the unequal de- 
velopment of the branches. The best time to observe this effect is in the leafless season, 
when the growth of the twigs is seen to be much influenced. Most affected perhaps are 
the poplars, and after them the willow, maple, elm, buttonwood, hickory, oak, and black 
walnut, in order. The cottonwood appears to yield very little to the influence. Find 
examples of this influence of prevaihng winds. If the wind observations have been kept 
since the beginning of the course, it now appears clearly that the west ones are the more 
frequent. 1. What percentage of all have you in that direction? 2. Is the wind effect 
on the trees in the same direction? The winds of observation for us are in the north- 
ern belt of westerly winds. They extend around the world between 30 and 60 degrees 
of north latitude. 

There is a similar belt in the southern hemisphere and in these two regions live the 
progressive and energetic races of the world. But we do not need to keep weather ob- 
servations to know that there are many other winds than westerlies here. In the lab- 
oratory exercise on the winds about areas of low barometer we found them blowing in 
evei-y direction, it is true, but with two common rules of conduct, so to say. 3. Wliat 
were these? 



53 




EXERCISE 14 —Wind Effect on Trees 

Our winds are prevailing from the same general 
direction. This is shown plainly by many trees. 

Go from the city westward in open country. 
Examine the trees from the southward or north- 
ward. When you think you perceive a wind effect, go to a point east or west of the tree. 
Is it now symmetrical? Sketch the tree from two directions at right angles. Observe 
and describe the wind effect on it. 

80. The diagram of planetary winds, Fig. 32, shows the average winds as they 
would blow on an earth without land. They are not real winds of the weather. None of 




Figure' 2!». Tlie winds as they woiili be on an ocean-covered globe 
our east winds show, for instance, since they are fewer than the west winds and disap- 
pear in the average. Also .all land winds are weaker than sea winds because of the f ric- 




Kigiire 30. World Isobars 



Calcutta Nagpur 

January 64 68 

February 70 74 

March 80 83 

April 85 88 

May 85 94 

June 84 86 

July 83 80 

August 82 80 

September 82 80 

October 80 79 

November 73 72 

December 65 67 



54 

tion of the surface of the land. So both trades and westerlies are much checked on lands. 
The summer and winter rainfall maps, Figs. 39 to 42, show ACTUAL winds of the 
world. 

EXERCISE U -Mon.soon Temperatures 

81. Construct curves of annual temperature at Calcutta and Nagpur, India, from 
the following data, using one square of the quadrille paper, vertically, for one degree, 
and two squares, horizontally, for a month. 1. Locate both places on Fig. 22. Calcutta 

is in north latitude 22.5, east longitude 88.5, Nagpur in 21 
north, 79 east. 2. At what date has Calcutta its maxi- 
mum temperature? 3. When does the maximum come 
at Ypsilanti? 4. When at Nagpur? The sun is in the 
zenith of Calcutta twice, June 7 and July 3; in the zenith 
of Nagpur May 25 and July 18. 5. About what time 
should we expect the maximum temperature at Calcutta? 
6. At Nagpur? You are to find out why the maximum 
temperatures in India come earlier than one would ex- 
pect. The following may help you. 7. From what di- 
rection does the wind blow in India in summer? 8. Upon 
what has this wind been resting before reaching Indi^? 
9. Does this make the summer of India warmer or less warm than otherwise? 10. 
What appears from the curve to have happened towards the end of May? 11. At what 
date did the summer monsoon begin to blow? 12. How did this afPect the Nag-pur ther- 
mometer? 13. Why does the maximum temperature come early at these two places? 
(Of course if something lowers the temperature at the time the maximum should occur 
the maximum is thereby made to come earUer.) 

82. The fact of rotational deflection may be simply stated thus: 
For a person in the northern hemisphere the earth turns from right to left. This 
causes all straight lines on- it to turn to the left. A body, or mass of air that starts off 
along a line holds its direction and therefore seems to turn to the right. (When we go 
into the southern hemisphere our point of view is changed, it is as if we looked at a 
picture from the back.) The earth and lines on it turn to the right and whatever moves 
off straight starting on a line, seems presently to turn off to the left from that line. The 
deflection is greatest at the poles and nothing at the equator. Why are such winds about 
a low barometer and their attendant circumstances in the air called a cyclone? Why are 
the winds and other conditions about an area of high barometer said to make up an anti- 
cyclone? Perhaps the most interesting thing about an anti-cyclone is that its winds are 
really governed by the same two rules of conduct as the cyclone. Both are illustrated 
on the diagrams of Australia and its seasonal winds. 1. When is the Australian wind 
system like a cyclone? 2. When is it like an anti-cyclone? 3. Is there not a difference 
each time? 4. Did you learn from Foucault's* pendulum why the trades have more 
southing than the westerlies have northing? Of course in the southern hemisphere the 
sun moves from right to left since the people there live, as it were, on the under side of 
the equator and see all our directions reversed, just as a man would who read diagrams 
from the back of the paper. Trace the winds of AustraUa on thin paper and look thru 
the tracing from the back side. Do not the winds go in to the right and out to the right? 

•FoucauU-s Pendulum; Youngr's Astronomy, p. 110; Report Cliief Signal Offlcer, 1885, part two. p. 131: 
Journal of Scliool Geography, 1899. p. 298. 



55 
MATER VAPOR, ( LOUDS, AND RAIN 

83. Water vapor is always present in the air. Even in the desert enormous quan- 
tities of water are always present in this form. Water vapor is transparent and invisible. 
The bluest sky, the clearest air contains it. Clouds are made of little particles of water, 
not of water vapor. Mist is cloud seen from the inside. Cloud is mist seen from the out- 
side. The steam inside the tea kettle is invisible as would be noted were the kettle made 
of glass. Close to the spout nothing is seen to issue. Only a little way off appears tlie 
mist of water particles called steam. It really consists of water drops condensed fr.-jm 
the steam by the cold air. Probably most of the water vapor in the air comes from the 
trade wind belts of ocean on either side of the equator. This map of the world, Fig. 31, 
shows the distribution of the Salter parts of the ocean surface. 1. What has the great 
saltness of these parts of the ocean to do with the supply of water vapor in the air? 




Fiffu 



li.n«(1 and the least salt is blank 



2. Are the trades growing warmer or colder as they advance? 3. Why? 4. Are they 
gaining in power to take up water? 5. Is the sky often cloudy in the trade winds? 
The percentage of cloudiness in Fig. 32 will enable you to answer the question. 




Figui'o 32. Lined areas have eloud.v sk.y more than half the time 



56 



84. Vapor is formed from water at all temperatures. The water particles are be- 
lieved to be in a state of rapid motion. Our thought of evaporation is that occasionally 
one of these particles near the surface plunges out into the air. This, as has been said, 
occurs at all temperatures, but naturally more at higher temperatures, when the parti- 
cles are moving faster. When this process has gone on long enough to cause a great num- 
ber of particles to exist in the vapor condition, it is not difficult to believe that occasion- 
ally one of these particles plunges back into the water. This should happen oftener as 
the space above the water becomes fuller of vapor. But presently there must come a 
moment when as many plunge in in a given time as emerge. At this moment the great- 
est possible amount of vapor exis^ts in the space and it is said to be saturated. If more 
heat be now apphed, the emergence of particles becomes more active and more vapor can 
be contained in the given space. If it be cooled, emergence is checked and the quantity 
of water vapor that can be contained in the space is diminished. In usual phrase, warm 
air has a greater capacity for water vapor than cold air, though the air has nothing to 
do with it; the same evaporation occurs into an empty space as into air and faster, per- 
haps because the air acts as a hindrance to the movement of the particles. 

85. Expei'iment has shown that air containing 4 grains of water vapor to the cubic 
foot is saturated at 50°. That is at that temperature 4 grains and no more of water 
could be evaporated into it. If cooled below 50' some of the vapor will take the form of 
dew or cloud. Experiments further show that a fall in temperature to 30° would con- 
dense about half the water vapor, while a rise to 70° would enable it to take up another 
4 grains to the cubic foot if it could get it. If it got no more water it would be said to 
have become drier in view of its increased capacity for moisture. For ordinary thought 
air is dry when it will dry other things. In this sense it is no part of drying air to take 
water away from it; on the contrary we might add two grains of water to the cubic foot 
while we raised it to 70° , and as it would still have a capacity of two grains of water it 
would be drier than it was at 50°. The effective moisture of the air is thus seen to be 
as much dependent on temperature as on water content. A better name for this sort of 
moisture is relative humidity. It is said to be 100 per cent when the air is saturated, 
as is air at 50° with four grains of water vapor to the cubic foot, but the same air 
heated to 70° without gain or loss of water would have a relative humidity of 50 per 
cent containing only four out of a possible eight grains. 

86. To illustrate actual values of relative humidity, the following table is inserted 
of average monthly temperatures and humidities observed at Detroit in 1898, at 8 a. m.. 
Eastern time: 



1898 



January ... 
February .. 

March 

April 

May 

June 

July 

August 

September, 
October.... 
November 
December. 



Tempera- 
ture 



26.2 
24 1 
55.3 
40.8 
59.4 
66.1 
69.7 
67.8 
61.7 
49.1 
34.8 
25.4 



Grains Vapor to 
1 Cubic Foot of Air 



Possibly Actually 



1.67 
1.53 
2.42 

2 95 
5.64 
7.11 
7 91 
7.48 
6.12 

3 97 
2. '8 
1 62 



1.44 
1 41 
1 94 
2.01 
3.61 
5.19 
6.17 
6 13 
4.83 
3 30 
1.95 
1 38 



Relative 
Humidity 



86 
92 
80 
68 
64 
73 
78 
82 
79 
83 
82 
85 



Pints Water 
Room 2 1 



3.9 

3.8 

5.3 

5 5 

9.2 

14.2 

16.9 

16.7 

13 2 

9.1 

5.3 

3.8 



57 



At the average temperature observed in January, 26.2", 1.67 grains of water vapor 
suffice to saturate a cubic foot of air, but as there were present only 1.44 grains the rela- 
tive humidity is said to be \ii or 86 per cent. If our room measures 42 by 34 by 14 
feet, multiplying the cubic feet in it by the grains of v.'ater to the cubic foot actually 
present in any month we shall get the number of grains of water present. Divide this 
by 7300, the number of grains in a pint, and thus verify one or two of the numbers 
in the last column. It seems surprising to find so large a quantity of water contained 
in the air. And the table shows that it is precisely in the summer months, when the 
sky is clear three-fourths of the time that the air contains most moisture, fully four 
times as much as in January when the sky is clear only a third of the time. Yet the 
summer air is drier, or better, the relative humidity is less, as the table shows. 1. How 
much vapor to the cubic foot can the January air still take up? 2. How much the Au- 
gust air? Strange as it seems the clear skies of August contain much more water vapor 
than the cloudy skies of February. The desert of Sahara has about as much water vapor 
in its air in summer as moist England, yet the desert temperature is so high that the 
air is dry, i. e., the relative humidity is not more than forty or fifty per cent. 3. What 
relative humidity is usual here? 

"Thus the air even above the dry ground of the desert contains a considerable 

amount of water vapor, brought from the neighboring seas 
and coast regions by air currents and by the diffusive power 
of the water vapor itself. The rainless character of the 
desert is caused, not by a lack of water vapor in the air, but 
by the absence of conditions leading to its condensation." 

89. The accompanying table contains the possible 
water contents at the given temperatures. 1. What was 
the water content in grains to the cubic foot of the air in 
the room at time of the experiment? 2. How many pints 
of water? 

Construct a curve from this ta,ble, using one square of 
quadrille paper, vertically, for 2°, and horizontally for ^ a 
grain of water vapor. 

KXER€ISE IG^ — Measuring- Moisture in tlio Air 

87. Take the temperature of the air in the room and of the water, which should have 
the same tempeiature, and will if it has stood in the room long enough. Dry the ther- 
mometer and again take the temperature of the air. Place a little water on the ther- 
mometer bulb and note what happens. Can you explain? The warmth of the mercury is 
being used to do work. What work? Now wrap the bulb with the cloth which is twist- 
ed into a rude wick and dipped into the water in the tumbler. The temperature falls 
and in five or ten minutes wiU reach its lowest point. Note the temperature reached 
and )5y the following diagram ascertain the RELATIVE HUMIDITY. 

Dry 73'\ wet 71 \ diiference 2", relative humidity 90 per cent. 
Human interest in the water vapor in tlie air is in relative humidity, which affects 
our comfort, and precipitation, which conditions life. 1. What are the conditions that 
lead to the condensation of water vapor? The fall of temperature that will be thought 
of as the cause, is due to some upward movement of the air and the expansion that 
must result. Such ascents occur in the equatorial regions, in cyclones and at mountain 
slopes. The last case has already been referred to. 2. In the first two what lifts the 
air? 3. Are there any movements of the air round about that cause the central air 
to rise? 





Possible 


Tempera- 


No. Grains of 


ture 


Water Vapor 




per eu. ft. 


0' 


0.54 


10'^ 


0.84 


20' 


1.30 


30 


1.97 


40 ■ 


2.86 


50" 


4.09 


60^ 


5.76 


70" 


7.99 


80 


10.95 


90'' 


14.81 


100" 


19.79 



58 




59 

It is now seen that there are several belts about the earth with rain conditions. One 
has a good deal of uprising air at all times. 4. Where is this belt? 5. What are its 
rain conditions? In another belt the air rises only at mountain slopes. 6. What sort 
of skies and vv^hat sort of lands should prevail at other points in this belt? 7. Which 
belt is it? Another has two different arrangements for causing the air to rise. 8. 
Which is this? Finally it is observed that two of these three belts occur necessarily in 
pairs. 9. Which ones? It is now possible to locate doldrum, trade-mountain and west- 
wind rainfall on the blank map. 

KXERCISE 17— Our Iricgiilar Rainfall 

88. Examine the table below of rainfall at Lansing, Michigan. 1. In what month 
is the rainfall greatest? 2. In what least? 3. By what per cent of the average month- 
ly rainfall (2.77 inches) is it least? 4. In how many years does the table show that 
the wettest month had less than the average rainfall? 5. What per cent of all the years 
is that? 6. Has summer or winter greater rainfall here? 7. Is that good or bad for 
our crops? Construct a diagram of four horizontal lines one above the other with their 
left ends in the same vertical line. The length of each line will represent the sum of 
the rainfall of three consecutive months, one for the three of greatest and one for each 
other group of three months. Let one-half inch in the diagram represent one inch of 
rainfall. 



Vi;ak 


Jan 


1m-:h. 


Mak 


Apr. 


May 


Jn.MK 


July 


Aug. 


Shpt. 


Oct 


Nov. 


Dkc. 


Yk'\r 


ISSO 


2 67 
2.27 
1.13 

98 
1-92 
!.59 
2 27 
3.36 

1 69 
1.67 
2.71 
1.07 

1 05 
1.84 
1.75 

2 66 
1 11 
3.62 

3 77 
2.05 
1.43 
1.6-1 

38 

1 54 
2.82 


1.85 

3 92 
2.59 

4 49 
3.24 

45 

1 64 

5 87 

1 74 
1.02 
1.85 

2 35 
1 64 
2.31 
1 67 
0.62 
1 08 

1 22 

2 16 

1 65 

2 84 
1 26 
0.56 

3 10 
1.53 


2.00 
2.14 
3 66 

34 
3.71 
6.40 
2.83 
1,30 
2.02 

1 14 
1.31 

2 48 
1.49 
3.78 
1.26 
1.14 
1.15 
3.20 

3 73 
3.17 
2.20 
2.97 
4.12 
1.52 
3.87 


7 06 
1.65 
1.85 
1.89 
2 12 

2 38 

1 51 
0.98 
1.29 
1.70 

3 23 

2 45 
2.40 
5 30 

3 31 
1.12 
2 05 
2.43 
2.04 
1.93 
2 30 
2.29 
1 69 

4 40 
1 70 


6.81 
2 97 
4.33 
6.31 
4 34 
1 85 
3.00 
2.12 
3.65 
3.86 
6 22 

1 84 
6.31 
4 OS 
6.51 
2.05 
2.67 
3.44 

2 16 
3.28 
4.25 

2 67 

3 91 
2.07 
3 60 


6 96 
3 66 
5 51 
9.91 

3 09 
5.88 
2.14 
1.45 
2.07 
3.65 

4 03 
2.26 
4.81 
7.19 
1.81 
1 24 
3.39 
3 68 
4.55 
1.15 
2.19 
3.75 
7.07 
4.16 
2.79 


6.00 
1.63 
1 84 
10.12 
3.24 
2.04 
0.64 
1.68 
1 80 
2.67 
52 
2.91 
3 08 
0.98 
1.45 
1.72 
7.10 
7., ^6 
1.46 
2.62 
5.09 
6 33 
6.99 
4.79 
2.15 


6 02 
2.05 
4.04 
0.21 
1.34 
6 75 
5.70 
0.93 
1 84 
0.18 
3.06 
5 27 
3.26 
73 
0.00 
5.38 
3 28 
2.0^ 
2.99 
33 
3 86 
3 24 
39 
5.68 
2.76 


4 13 
3 24 
1.07 
3.37 

2 71 

3 46 
6 05 
5.53 
2.06 
0.83 
2.39 
1.37 
2.80 
2.34 
2.76 

86 
6 27 
0.91 
2.53 
2.24 
1.27 

1 88 

5 66 
3.92 
2.35 


2 84 
5 60 
3.10 

3 64 
6,13 

3 60 

1 15 

2 28 
3.03 
75 

4 96 

77 
1.00 
4 55 

1 98 

87 . 
0.87 
2.14 
3.66 
3.11 
3.51 
4.87 

1 65 
1.99 
2.20 


2.38 
4.39 
1.75 
4 08 
1.60 
3.05 
1.37 

2 06 

3 3i 
2 59 
2 91 

4 39 
2.61 

2 46 
1.05 

3 91 

2 98 

3 39 

2 60 
1 86 

3 88 

1 32 

2 30 
1.45 
07 


66 

1 76 
1 30 
0.93 
2.77 
2.86 
1.22 
2.51 
1 25 
2.68 
1.35 
1 89 
1 61 
3 96 
1.14 
5.83 
0.72 
1.95 
1.27 
1.61 
0.47 
2.90 
2.32 
2,06 
1.27 


49 


18S1 


35 


1882 


•)-> 


1SS3 


46 


18S4 


36 


1885 


40 


1SS6 


29 ^^ 


1887 


30 


1888 


26 


1889 


23 


1890 


34;^ 


1891 


29 


1892 ... 


32 


1893 


39 J^ 


1894 


25 


1895 


27 


1896 


33 


1897 


35 


1898 : 


3i 


1899 


25 


i9nn ... 


33 


1901 


35 


1102 


37 


1903 


37 


1904 


27 






;\\"crn;^e 


2.00 


2.11 


2.52 


2.44 


^3.77 


3 93 


3.45 


2.84 


2.88 


2 73 


2.55 


1 93 


33 1 







At Boston the annual rainfall is 45.4 in. 
distributed as in the table. 

Fill out the Lansing: columns. 



BOSTON 

Inches Per Ct. 

Feb., Mar., Apr., .11.4 25 

May, June, July 10.5 23 

Aug., Sept., Oct 11.5 25 

Nov., Dec, Jan. 12.0 27 

45.4 100 



LANSING 
Inches Per Ct. 



60 



MAPS 

89. The ball shape of the earth makes it impossible to draw maps correctly on any- 
thing but a ball. Any map on a flat paper is necessarily somewhat distorted. A famil- 
iar illustration is the cracking of a half orange peel that has been removed intact in its 
natural form, on pressing it down on the table. Another good one is had when you at- 
tempt to wrap a ball up in paper. Flat paper cannot be accomodated to it. Such sur- 
faces — those to which a flat paper cannot be adjusted by merely rolhng or wrapping, are 
known as warped. A trial, however, will quickly show that for a small part of the earth's 
surface, the disagreement between the ball surface and a plane is not very great. A 
circle of paper half an inch in diameter, placed upon a six-inch globe, comes near enough 
to resting upon the surface to make the part of the map traced through it fairly identi- 
cal with that on the globe. Such a circle on that scale is 660 miles ia diameter, about big 
enough to contain all the Great Lakes and the country about them; the whole of the Brit- 
ish Islands, or cmy European country except Russia, Sweden, or Norway. So there are 
many maps in which the distortion is of little account. Maps of whole continents, how- 
ever, are necessarily somewhat distorted, and no map of the world, or even a hemisphere, 
can help misrepresenting shapes and sizes. Different methods of map-drawing, or "pro- 
jection", as it is called, are devised to render maps of large areas available for various 
purposes, one considering the needs of the navigator, another that of persons wishing to 
compare areas, and others wishing a map that gives a comparative view of the whole 
world at once. The study of projection utilizes the highest skill of the mathematician. 
But simple constructions will give some good results. The device by which maps are 
drawn on the globe is the use of latitude and longitude, parallels and meridians. Some- 
thing of the sort is rendered necessary by the fact that a ball has neither a beginning 
nor an end. 

90. Meridians and parallels cover the surface of a globe with a network of meshes. 
These are said to be ten-degree meshes when meridians and parallels alike are ten de- 
grees apart, four degree meshes when these are four degrees apart, and so on. On most 
maps meridians and parallels are the same number of degrees apart, but many globes 
have fifteen-degree spaces between meridians and ten-degree spaces between parallels, 
for purely mechanical reasons. The shapes of the meshes are different in different lati- 
tudes. If meridians and parallels are the same number of degrees apart what is the 
shape of the enclosed meshes near the equator? What near the poles? What at inter- 
mediate latitudes? 

EXERCISE 18 
To draw a map we must first prepare the right net. Let us try to draw Borneo, 
using a five-degree mesh and making it a ten-millionth as long 
or as wide as the real island. 



The northern parallel is 10" north, the southern one 5" 
south. 1. How many spaces shall we use in latitude? The 
western meridian is 105° east, the eastern one 120" east. 
2. East of what? 3. How many spaces shall we use in longi- 
tude? 4. How many meshes wiU there be in the finished 
map net? The following table gives the dimension of the ten- 
degree meshes of the actual world in inches, full size; 




Figure 34. Borneo 



61 



Diuietisions of the Earth in inches 




10° on 


slant height 


Lat. 


parallel 


for cone 





43,821,397 


infinite 


10 


43,159,992 


1,424,078,254 


20 


41,190,721 


690.100,982 


30 


37,982,128 


435,243,224 


40 


33,615.524 


299,636,802 


50 


28,223,172 


211,093,3.57 


60 


21,965,743 


145,324.237 


70 


15,032,175 


91,655,436 


80 


7,634,237 


44.415,856 


Ten cleg: 


■ees of latitude 


i.s 13. 717. '.Ml in. 



The table gives for every 10" of latitude the 
space between meridians and the slant height of a 

cone that touches the Earth at that parallel. On 
the 80th parallel for instance 10° longitude is 7,634,- 
237 inches long, and the slant height of a cone touch- 
ing the Earth on latitude 80° is 44,41.5,8.56 inches. 
5. How many inches is a ten-millionth of ten 
degrees on the tenth parallel? 6. How many a 
ten-millionth of ten degrees on the meridian? 
7. How many five degrees in each case? Let us 
make the meshes squares of two inches on .an edge. 
Because we are not using the exact values found, the scale of our map is not 1 : 10,000,- 
000, but 1 : 10,936,987. Do you see how that works out? 8. Construct a six-inch square 
and subdivide it into nine equal squares. 9. Number them as in the cut and make an 
outer frame two-tenths of an inch outside of the six-inch square. 10. Now draw 
Borneo on it faintly with a verj^ soft pencil. Put dots in the middle of each mesii. They 
will help you draw the coast lines across the meshes. Notice where the coast line cuts 
the meridians and parallels and make these crossing points right before attempting to 
draw the coast line. When the coast hne looks as good as you can make it, darken it. 
On the finished map the coast should show more plainly than any other line. Parallels 
and meridians should be as fine and faint as you can draw them. They are only helps, 
the outline of the country is the important thing. 

EXER€ISE 19 

91. To make a ten-degree map net for North America on the scale of a hundred- 
millionth. Materials. You need now two drawing pencils, a HHH for points and lines, 
and a B for outlines of coasts or boundaries. Both need special sharpening to long, 
needle points, very much sharper than any point we use on a pencil for writing. You 
cannot make a good map without this special pencil point. Also a flexible paper rule 
divided into tenths of an inch and perforated with a small hole at the zero point for the 
point of the pencil so that you can draw circles up to a radius of 12 inches with it. A 
siiiall celluloid triangle will be very useful. 

1. As Fig. 35 shows, the northern latitude is 70°, 
the southern 10°. 2. What is the middle latitude? 
3. According to the table in paragraph 93, the tangent 
to the real world at latitude 40° is 299,636,802 inches 
long. 4. How long shall we take that? What is our 
scale? 5. How do we get three inches? 6. On a sheet 
of the blank paper detached from the back of the 
book, draw a straight line parallel to the long edges of 
the sheet through the middle. Construct a rectangle 
three inches high and four inches wide near the middle 
of your paper so as to be bisected by the long middle 
line. 7. At middle of the frame place a dot. Call tiie 
line the 100th meridian and the dot its intersection 
with the 40th parallel. 8. Put another dot on the line 
three inches north of this dot. Put a faint little circle 




Fiffiue 35. Net for North America 



62 

about this upper dot and call it the center of circles. 9. From this center draw a circle 
with the three-inch radius. It must pass through the lower dot. Why? The circle 
so drawn represents the fortieth parallel of north latitude. 10. We need other dots 
above and below 40" along the middle meridian for every tenth degree of latitude: 50', 
60^ and 70°, and 30°, 20°, and 10°. 11. How long is ten degrees of latitude? See 
taWe in paragraph 93. 12. How long shall we make it on our scale? 13. Place those dots. 
The table also tells us how far apart ten degree meridians are on the fortieth parallel. 

14. How far shall we take them? Shall we call it 33 or 34 hundredths of an inch? 

15. Call our middle meridian the 100th west of Greenwich and place dots for meridians 
over to 30° west and to 170 west latitude. 16. Now from the center of circles draw arcs 
of circles through all the dots along the middle line. Draw only those parts of the 
circles that can be drawn within the frame. 17. The meridians pass through the dots 
on the fortieth parallel and the center of circles, but only that part of each is to be 
drawn which lies within the frame. 18. Number as in cut and add outer frame. 

EXEKCISE 20 

92. To draw Europe on a scale 1 : 50,000,000. Northernmost latitude 70° N, south- 
ernmost 30°N, mid-latitude 50'N. From the table in paragraph 90 we get values for 
our scale of 10° latitude, 0.875 inches; radius for 50°, 4.22 inches; 10° longitude on the 
50th parallel, 0.564 inches. NOTE: These nets should be made of very fine lines.v so 
fine as to be hard to see when held at arm's length. Beginners invariably make 
them too dark, too heavy, and above all, too wide; for they attempt to draw with 
a pencil point such as they write with. This work requires a pencil with a needle 
point, altogther too sharp and thin to write with. The first thing to do at each 
of these exercises, therefore; is to sharpen the pencil. It will then need very light 
handling to preserve the point. Attention to this detail makes it possible to meas- 
ure to hundredths of an inch. 

Direction: — 1. Draw a four-inch square near the bottom of the paper. 2. Number 
the center of it 50.° . 3. Draw the 20th meridian through the center, the full length of 
the paper. 4. Mark also the 70°, 60°, 40°, and 30° points along the meridian, with the 
value of the 10° space given above. 5. Put a dot on the extended 20th meridian 4.22 
inches above the 50° point. This is the center of circles. 6. From this center draw 
arcs within the frame through all points marked. Through the 50° point, make the arc 
across the whole sheet of paper, {. e,., not merely within the frame as on the other cases. 
7. Along this 50th parallel lay off spaces of ten degrees of longitude, five to the west 
and five to the east of the 20th meridian. 8. Connect each of the points with the center 
of circles with the ruler edge, and draw that part of the lines that falls within the 
frame. 9. Number meridians and parallels and enclose in a 4-^-inch square. 10. To ac- 
custom your eye to the outline of the continent of Europe make a tracing of it on rice 
paper from Fig. 6. 11. Draw Europe freehand on your net from Fig. 8. 

EXERCISE 21 

93. To draw South America on a scale 1 : 100,000,000. From 20°N, to 60°S. Wliat 
is the middle latitude? Take the values of radius for 20° and the ten-degree spaces from 
the table in paragraph 93. Frame measures 4 inches in latitude by 3 inches in longitude. 
As this continent is in the southern hemisphere, the meridians converge southward, so 
the frame should be drawn near the top of the paper, and the center of circles falls on 



63 

the mid-meridian extended, below the frame. This mid-meridian is 60° W. Outline of 
continent to be first traced and then drawn on the net. , 

EXERCTSE 22 

94. To draw Africa. Scale 1 : 60,000,000. 1. The middle meridian (20° E) and the 
equator may be drawn as straight lines that cross in the middle of the paper, at right 
angles, and each about 6i inches long. 2. Complete the square of which these two lines 
are diameters. It is the frame. 3. Lay off four ten-degree spaces along the 20th merid- 
ian on each side of the equator and draw straight lines parallel to the equator through 
these eight points for the parallels. 4. Lay off ten-degree spaces (longitude) along the 
equator, four to the east and four to the west. 5. Do the same on each parallel, using 
always the ten-degree space of longitude for that parallel, which is taken from the table 
and reduced to our scale as usual. 6. Draw curves through these points with the help 
of the ruler. Number and draw map as usual. 

95. Scales. 1. How many inches in a mile? 2. A map on the scale 1 : 100,000,000 
has one inch where nature has a hundred million inches; how many miles is that? 
3. How many miles to an inch on a map of the scale 1 : 100,000,000? 4. How many miles 
to an inch on our map of Europe in paragraph 92? 5. How many on the map of Africa 
in paragraph 94? 6. How many miles to the inch on a scale of a millionth? 7. If a map 
has 395 miles to an inch, what is its approximate scalle ratio? 8. What is the scale ratio 
for a map with a hundred miles to the inch? 

EXERCISE 23 

96. To draw New Zealand on the scale 1 : 8,000,000 with a two-degree mesh. 1. Ten 
degrees on the meridian to that scale is 5.46 inches. How much is two degrees? 2. Sim- 
ilarly take from the table the values of two degrees on the 40th and 50th parallels. 

3. Draw the 172nd meridian through the middle of the paper parallel to the long edges. 

4. Lay off eight spaces along its middle portion, each 1.094 inches long. What do these 
spaces represent? The bottom one is to be numbered 50° . NOTE: When there is less 
than 20° of latitude in a country the parallels may be drawn as straight lines par- 
allel to the equator without much error. 5. Draw straight lines through the division 
points on the meridian and at right angles to the meridian, extending two inches to the 
left of it and three to the right. 6. On the 40th parallel, toward middle of net, lay off 
spaces of 0.84 inch, two to the left and three to the right of the 172nd meridian. 7. On 
the 50th parallel lay off similar spaces of 0.706 inch. 8. Draw meridians through these 
points and number. 9. Draw New Zealand from Fig. 36. 

97. Maps of most moderate-sized countries may be drawn as in exercise 23. The 
following lines show how to draw the parallels as curves. 

EXERCISE 24 

Repeat Nos. 1 to 4 of paragraph 96. 5. Number the dots along the meridian, put- 
ting 50° at the bottom and 34° at the top. 6. Draw perpendiculars through the 40° 
and 50° points, two to the left and three to the right of the 172nd meridian. 
7. Lay off divisions along these two lines as in numbers 6 to 7 of paragraph 96. 8. Draw 
meridians and number 168° to 178° E. 9. Lay your ruler across the 172nd meridian, at 
right angles to it at the 36th parallel. 10. Draw a short line for about half a longitude 
space on each side of the meridian. 



64 




To make this wholly clear we may 
add that the line so drawn will cross 
the 172nd meridian at right angles and 
will extend about half way to the near- 
est meridians right and left. 11. Sup- 
pose you end the line so drawn about 
half way between 172 and 174. Do not 
lift the pencil point from the paper 
there, but rather bear on it lightly so 
that it forms a pivot about which you 
then turn the ruler edge, lifting the 
left end and lowering the right slight- 
ly until the ruler is now perpendicular 
to the 174th meridian. 12. Now draw 
from the point where the pencil pivot- 
ed across the 174th meridian and on 
half way to 176. In this way a hne is 
drawn that looks very like a curve and 
crosses all the meridians at right an- 
gles. 



171 178 176 

Figure 36 



TEJtPERATURES 

98. The usual data for temperatures are isothermal lines. They always represent 
temperatures reduced to sea level, though practically all geographies and physical geog- 
raphies fail to mention that fact. .It is the best way to draw isothermal lines. All 
meteorologists know it and how to use such a map, but teachers and school children do 
not. If a teacher tries to learn from such a map the temperature on the summit of the 
Himalayas she finds it to be 50" or 60° in winter and 80° or 90° in summer. Of course 
she knows there is ice and snow up there the year around and the map cannot be right. 
She does not know it has to be corrected for altitude before any of its indications become 
those of the actual surface, and finding it mentally indigestible she wisely lets it alone 
in all her work. Koppen's map on the contrary is for actual surface temperatures, and 
while it suffers certain defects inherent in all such maps, it does give a rough idea of the 
actual temperatures all over the surface of the earth and a fairly accurate one in those 
regions where men live. Note what our diagram indicates on the Himalayas. 

99. TEMPERATUKES. NORTH AMERICA. Figure 38 

1. What ocean shores are always cool? 2. What ocean has shores with hot summer 
and cool winter? 3- What parts of Mexico are always hot? Why? 4. What temper- 



65 

perature has Mexico City? 5. What temperatures prevail in most of Canada? In most 
of the United States? In Mexico? 6. What sort of summers and winters has Florida? 
Maine? 7. What three types of temperature occur on the California coast? 8. Name 
three large cities with hot summer and cool winter. 9. Name two with mild summer 
and cool winter. 10. Name one with hot summer and mild winter. 

100. TEMPERATURES. EUROPE. Figune 37 

1. State England's summers and winters. 2. Name other countries of similar tem- 
perature. 3. State the temperature of Portugal. 4. Compare North Sea-Baltic countries 
with the Mediterranean countries. 5. What different sorts of summers occur in Russia? 
Winter? 6. What temperature type is most widespread in Europe? 7. Name three 
large cities with hot summers and cool winters. 8. What ones can you name with mild 
summer and cool winter? 

101. TEMPERATURES. ASIA. Figure 37 

1. What parallel approximately bounds most of cool Asia? 2. Locate and bound 
other cool regions. 3. What parallel bounds hot Asia? Exceptions? 4. Where are the 
hot-and-cool regions? 5. Explain the interruptions. 6. Name three countries that have 
hot summers and cool winters. 7. Where is it mild the year around? 8. State the tem- 
perature of India, China, and Japan. 

102. TEMPERATURES. AFRICA. Figure 37 

1. Locate and bound and explain the mild areas. 2. Locate and bound the hot-and- 
cool regions. 3. Give the parallels approximately bounding the hot regions. 4. Where 
in Africa are the cool winters and mild summers? 5. Explain and tell whether people 
probably live there. 

103. TEMPERATURES. SOUTH AMERICA. Figure 38 

1. Locate and bound and explain the "always mild" regions. 2. Locate and bound 
the "always hot" regions. 3. Where, if the scale of the map were large enough to show 
it, might there be thin lines or dots of "always cool"? 4. What percentage of South 
America has hot and cool seasons? 5. Name a large city with hot summer and cool 
winter. 6. State the temperatures of Bogota, Lima, Rio Janeiro and Caracas. 

104. TEMPERATURES. AUSTRALIA. Figures 37 and 38 

1. Where are the hot regions? 2. What regions are always mild? Why? 3. What 
towns have hot summer and cool winter? 4. State the temperatures of New Zealand. 
5. State the temperatures of Melbourne, Sydney, .and Wellington. 

105. RAINFALL OF JUNE, JULY, AND AUGUST. NORTH AMERICA. Figure 40 

1. Describe the two areas of scanty rain. 2. What national names might naturally 
be given to the two nearly separate parts of the area of abundant rain? 3. Why does 
it rain abundantly in Alaska and scantily on the Californian coast? 4. How much of 
North America has sufficient or abundant rain at this season? 5. Describe the distri- 
bution of rain in Alaska and explain with the help of the winds and a map showing 
mountains. 6. Describe the rainfall of the Pacific coast in three items. 7. Why have 
the West Indian and Arctic islands rainfall so different? 



66 



TEMPERATURE REGIONS 




SHADE 
Black 

Vertical lines 
Horizontal lines 
Slanting lines 
Blank 



Figure 37 
LEGEND 

TEMPERATURE DETAILS 

- Always Mild . . - - Hottest month averages under 

68° coldest over 50° 
Alvi'ays cool - - Warmest month averages under 50° 
Always hot - - Coolest month averages over 68° 
Hot summer and cool winter Averaging over 68° and under 50"* 
Summer hot and winter mild toward the equator; 
Summer mild and winter cool toward poles. 



•For at least a month each. 



67 



OF THE WORLD 




Figure 38 



Redrawn from Koppen as given by Ward in Bulletin Am. Geog. Soc, July, 1905, with slight al- 
terations in the United States. 

It will help the eye in reading these diagrams if the student will now shade the Cool areas a very 
pale blue with a colored pencil,* the Hot areas a pale red, and the Hot and Cool season regions with a 
red line on the first, fifth, and ninth spaces between the slanting lines and so on with a blue one on 
the third, seventh, and eleventh, thus making' lines alternately red, white, blue, white and so on. 

In coloring the Cool areas do not overlook a small one between the thirtieth and fortieth parallels 
of north latitude. If the map were large enough to show them there would be other blue dots and 
lines on various other mountain peaks and crests. 



•The six School Crayon.s 
tinting- maps. 



in assoi'ted color.s .sold in a iio.\ by the American Lead Pencil Co.. are excellent for 



68 



RAINFALL OF THE WORLD IN JUNE, JULY, 




Flgui'* 39 



SHADE RAINFALL 

Ruled lines - Abundant 



Dots 
Blank 



Sufficient 
Scanty 



DETAILS 

More than ten inches of rain and melted snow in the three 

months. 
From six to ten inches in the three months. 
Less than six inches in the three months. 



69 



AND AUGUST (INCLUDES MELTED SNOW) 




Figure 40 



After Supan. 

It will add much significance to the diagrams if the student will nmx tint with pale red the shad- 
ed and dotted areas north of the tropic of Cancer, 23^,2 north, as symbolic of summer or warm-season 
rains, and with pale blue the shaded and dotted areas south of the tropic of Capricorn, symbolizing 
cold-season or winter rains. That the zone within the tropics remains uncolored means that it does 
not have true summer and winter. 



70 



RAINFALL OF THE WORLD IN DECEMBER, JANUARY, 




SHADE RAINFALL 

Ruled lines - Abundant 



Dots 
Blank 



Sufficient 
Scanty 



Figure 41 
LEGEND 

DETAILS 

More than ten inches of rain and melted snow fall in the three 

months. 
From six to ten inches in the three months. 
Less than six inches in the three months. 



71 



AND FEBRUARY (INCLUDING MELTED SNOW) 




Figure 42 



After Supan. 

It will add much significance to the diagrams if the student will now tint with pale red the shad- 
ed and dotted areas north of the tropic of Cancer, 23%° north, as symbolic of summer or warm-season 
rains, and with pale blue the shaded and dotted areas south of the tropic of Capricorn, symbolizing 
cold-season or winter rains. That the zone within the tropics remains uncolored means that it does 
not have true summer and winter. 



72 

1(»0, RAINFALL OF DECEMBER, JANUARY, AND FEBRUARY. NORTH AMERICA. Figure 42 

1. Describe the rainfall of the Pacific coast. 2. What rainfall characterizes the 
southern part of the continent at this season? 3. What part and how great a part of 
North America has scanty rainfall? 4. To what sort of situations on the continent are 
the abundant rains limited? 5. What American states get their rain mostly in winter? 
6. In what sort of situations does most of the sufficient rain occur? 7. Name some 
states which seem to be characterized by summer rain. 

107. RAINFALL OF JUNE, JULY, AND AUGUST. EUROPE. Figure 3!) 

1. Name six regions of abundant rain. 2. Explain each of them. 3. What is the 
cause of the rainfall of Russia? 4. Describe the rainfall of Spain, Italy, and Germany. 
5. What European sea has little rain on its shores? 6. What two countries have only 
scanty rainfall at this season? 

108. RAINFALL OF DECEMBER, JANUARY, AND FEBRUARY. EUROPE. Figure 41 

1. Describe six regions of abundant rain. 2. How much of Europe has scanty rain 
at this time of year. 3. Compare the distribution of rain in the Scandinavian, Iberian, 
and Balkan peninsulas and in Asia Minor. 4. What country has its greatest drought at 
this season? 5. What country comes nearest to having the same rainfall summer and 
winter? 

lOi). RAINFALL OF JUNE, JULY, AND AUGUST. ASIA. Figure 39 

1. How much of the continent has abundant rain? (Include the islands.) 2. How 
far inland does the abundant rainfall extend? (The north and south measure of each 
map mesh is 690 miles.) 3. Describe the shape, location, and size of the large area of 
sufficient rain. 4. What is the grade of rainfall of the greater part of the continent at 
this season? 5. Locate the dry parts of Asia. 6. How does this resemble the distri- 
bution of rainfall in North America? 7. From what body of water did the Japanese 
rains evaporate? 

110. RAINFALL OF DECEMBER, JANUARY, AND FEBRUARY. ASIA. Figure 41 

1. What four points on the continent have abundant rain? 2. What other Asiatic 
regions? 3. Does this resemble the distribution of rainfall in North America in winter? 

4. Why has India so much less rain than in summer? 5. From what waters did the 
Japanese rains of this season evaporate? 6. What two populous regions have sufficient 
or abundant rains at aU seasons? 

111. RAINFALL OF JUNE, JULY, AND AUGUST. AFRICA. Figure 39 

1. Explain the rains of Madagascar. 2. Explain the southernmost rains of the con- 
tinent. 3. Where are the northernmost rains? 4. What rainbelt do they belong to? 

5. Why doesn't it rain in northwest and southwest Africa? 

113. RAINFALL OF DECEMBER, JANUARY, AND FEBRUARY. AFRICA. Figure 41 

1. Explain the northernmost rains. 2. Why are there no rains at the Cape of Good 
Hope? 3. What causes the rains of southeast Africa? 4. Explain the shift of the Dol- 
drum rains since July. 5. Where is there abundant rain in both seasons? 6. In what 



73 

month must the Nile be in flood? Allow a month or two for the water to get from the 
equatorial swamps into the river channels. 7. Do you perceive three African ilhistra- 
tions of seasonal migrations of rains? 

113, RAINFALL OF JUNE, JULY, AND AUGUST. SOUTH AMERICA. Fi^ie 40 

1. Describe four patches of abundant rain. 2. What patches of trade-wind rain are 
there? 3. Which are clearly westerly wind rains? 4. How much of the continent has 
scanty rain? 5. Wliat parts of it? 6. Why is there so little rain on the Peruvian coast? 

114. RAINFALL OF DECEMBER, JANUARY, AND FEBRUARY. SOUTH AMERICA. Figure 42 

1. How much of the continent has abundant rain? 2. Describe the rainfall of the 
Argentine Republic. 3. Describe the rainfall of Brazil. 4. Describe and explain the 
rainfall of Peru. 5. What regions have abundant rains in both seasons? 

115. RAINFALL OF JUNE, JULY, AND AUGUST. AUSTRALASIA. Figures 39 aiul 40 

1. Is this summer rain? 2. What wind belt yields most of it? 3. Why has the 
southeast corner more rain than the land just west of the coast? (Compare eastern 
United States in Fig. 45.) 4. Why has the southern island of New Zealand more rain on 
the west than on the east? 5. Why not the northern island? Notice the relief of New 
Zealand. 

110. RAINFALL OF DECEMBER, JANUARY, AND FEBRUARY. AUSTRALASIA. Figs. 41 & 42 
1. Has Australia any westerly-wind rain at this season? 2. Has New Zealand? 
3. How may we know ? 4. What are the two types of rain in Austraha and where does 
each occur? 5. In what season has Australia most rain? 6. Is it like Asia in that? 

117. PLANT REGIONS. NORTH AMERICA. Figure 44 

1. What per cent of Canada is summer forest? Of the United States? 2. Wliat 
three other types of vegetation occur in the United St^s in order of area occupied? 
3. Where shall a New York man go to get quickest to a wet tropic forest? 4. How 
much desert and grass-land has the United States?* 5. What do we call the grass-lands 
of North America? 6. Why are they not as populous as the summer forests? 7. Explain 
the forest of southeastern United States. 



° It lia.s long- been a vexed question as to the alisence of trees in a soil which seems to be most 
suitaljle for their development. Probably the most Mncient explanation was the occurrence of praii-ie 
rires, l)ut it seems evident that some general natural condition rather than an artificial one is respon- 
siljle for sucli an extensive area. A possible explanation is as follows: The extensive plains of the 
West develop tlie strong- and dry winds Avliich in-evail over the prairie region, and this bring-s about 
e.xti-emes of heat and drouth, in spite of the charactei' of tiie soil. In sucli conditions a tree in a gen- 
min.ating- condition could not establish itself. The prairies, therefore. rei>re.sent a sort of bro.-id beach 
between the Western plains and the Eastern forests, Tlie eastern limit of the prairie has probably 
depended uiion the limit of the dry winds, wii-ich are g-radually modified as they move eastw.-ird, until 
tiiey cease to \>e unfavorable to forest growth. The forest does not beg-in abiuptly upon tlie eastern 
limit of the prairie, but appe:ii-.s fli-st a clump of trees, with interspersed meadows, and finally as ,a 
dense forest ni.ass. Of course, the forest display of the eastern boi'dei* of the prairie has been im- 
mensely interfered with by man. — Coulter. Plant Kcl.itions, jiages 2.'i(!-8. 



74 



PLANT REGIONS 




SHADE 

1. Black 

2. Black Spots - - - - ' - 

3. Dots 

4. Black Bars 

5. Black Triangles ... - 

6. Circles 

7. Stars of sixty degrees Tike a snowflake 

8. Broken lines 

9. SmaU Dots ----- 



i'igiu'e 43 

LEGEND 

VEGETATION 
Wet Tropic Forests 

Wet Season Tropic Forests 

Tropic Open Woods 

Sub-Tropic Wet Forests 

Leathery Leaf Thickets 

Summer Forests 

Alpine Plants 

Grass Land or Steppes 

Tundra 



75 



OF THE WORLD 




Figure 44 

After Schimper. DETAILS 

1. Warmth and rains at all seasons. Air plants abound. Forests are impassable. 

2. Less dense. A season of drought compels trees to drop their leaves and rest. Along the streams 

this does not happen. Temperature still high. Air plants numerous. 

3. Warm, but severe seasonal drought allows only isolated trees in broad expanses of bush or grass. 

Continuous forest along streams only. 

4. Less luxuriant than near the equator. Evergreen; but interspersed are trees that drop their 

leaves, not in dry, but in a cold season — winter. 

5. Always in regions of winter rain, 30^ or 40^ from the equator. The leaves are tough enough to 

withstand considerable summer drought. Oleanders are typical. Trees moderate sized, gnarled 
and less abundant than shrubs. Trees stunted by getting water enough for growth in the cold 
season only. 

6. Moderate rain and winter cold severe enough to arrest growth or cause leaves to fall. These for- 

ests may usually be traversed without hewing a path, but have fine trees which get their growth 
in a moist summer. 

7. Stunted plants that live on cold, windy mountain summits. 

8. With forests along streams. Increasing drought changes grass land to steppe, the steppe to desert. 

9. Low shrubs and herbs that imperfectly cover the ground which is frozen ten months in the year. 



'76 

118. PLANT REGIONS. EUROPE. Figure 43 

1. What two types of forest occur in Europe? Where? 2. What percentage of 
Europe is in summer woods? 3. Distinguish steppes from grass-lands in Hungary and 
Russia. 4. Give reasons. 5. What North American types of forest are wanting? 

119. PLANT REGIONS. ASIA. Figure 43 

1. To what rainfall does the wet tropic forest correspond? 2. What Asiatic coun- 
tries ha-ve deserts? 3. State the plant regions of China and India. 4. State the plant 
regions of Japan and Dutch East Indies. 5. What percentage of Asia has summer for- 
ests? What countries? 6. Where are the leathery leaf thickets? 

120. PLANT REGIONS. AFRICA. Figure 43 

1. What type of forests are lacking? Why? 2. Equatorial Africa has many rivers. 
What report might a traveler along them make of the plant type there? 3. What is the 
real type? Why? See Fig. 10. 4. In what other parts of the world have we found the 
Cape Town vegetation? 

121. PLANT REGIONS. SOUTH AMERICA. Figurtj 44 

1. What is the only plant type missing? Why? 2. What are the plant regions of 
Chile? 3. What those of the Argentine Republic? 4. In what wind belts are the wet 
tropic forests? 5. What large country has most of the tropic forests? 6. Why are 
alpine plants so much more abundant than in North America? 

122. PLANT REGIONS. AUSTRALASIA. Figures 43 anid 44 

1. What sort of forests prevail in the thickly settled parts of Australia? 2. Where 
are the leathery leaf thickets found? 3. Explain the forests of the north. 4. Why 
should New South Wales and the southern island of New Zealand have plant regions so 
contrasted in position? 



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